ISSN 2399-1542 ISSUE 108
MATERIALS RESEARCH SOCIETY MRS are dedicated to the promotion of materials science, through communication and engagement. Dr Todd Osman discusses the organisation’s successes and shares his hopes for the future of materials research.
AMERICAN CHEMICAL SOCIETY
EUROPEAN MATERIALS RESEARCH SOCIETY
Dr Donna Nelson, Immediate Past President, explains why she is passionate about communicating the importance of science to the public.
President, Dr Luisa Torsi, outlines her plans for the society and details how they 3 Research Features have fostered a sense of community in this interdisciplinary research area.
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This Issue
TO ISSUE 108
The impact of science is evident in our everyday lives. The technology we use, the clothes we wear, the way we communicate are all products of painstaking research. But its influence is even wider than this: by investigating the birth of our universe or the nanostructure of atoms, scientists continue to shed light on the undiscovered corners of our world. The researchers in the issue are spread across the varied areas of maths, physics, chemistry, and materials. Whether it involves a new technique for harnessing solar power or the ability to watch molecular changes as they happen, their work highlights the importance of continued discovery. This is also a key message from the Executive Director of the Materials Research Society, Dr Todd Osman. He speaks to us about the world-class research taking place within the sphere of materials science and how it promises to improve quality of life for people around the world. This relevance of science to everyday life is something that fascinates Dr Donna Nelson from the American Chemical Society. Passionate about communicating science, Dr Nelson tells us how she collaborates with Hollywood to give a more accurate and high-profile depiction of science. The European Materials Society also aims to raise the profile of materials science and Dr Luisa Torsi, the President, explains how the society acts as a focal point for this highly interdisciplinary area. The researchers featured in this issue push at the boundaries of our understanding – read on to get to grips with their fascinating work.
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CONTENTS
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06 10 16
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20 26 30
54 58 62
MRS: The strange matter of materials science
The REEMS Programme: discovering untapped talent
Failure under complex strains and stresses: fracture and fatigue in advanced materials Functional textiles driven by transforming NiTi wires
Understanding glassy dynamics Electronic behaviour in magnetic matter: insights from femtosecond and terahertz spectroscopy
34 38 42 46
How new technology is stopping fire in its tracks
Sparks fly in nanoscale engineering ACS: Taking chemistry to Hollywood
A coherent look at synchronised reactions
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An introduction to precise macromolecules based on molecular nanoparticles Creating ‘molecular movies’ with ultrafast Raman spectroscopy
82 86
A star is born: understanding the physics of star formation Video Communication: The stats you need to know
Metal Organic Frameworks – the future of solar energy? Kinetic descriptions – a mathematical bridge to better understand the world
66 70 74
E-MRS: Rewarding collaborative materials research
The physics of extreme matter: how did the universe begin?
IceCube: experimental particle astrophysics with high energy neutrinos
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Galactic nucleosynthesis: the onset of element production in our galaxy
58 5
Thought Leadership
MRS: The strange matter of materials science
Materials science shapes the world as we know it. Dr Todd Osman has dedicated his career to advancing this interdisciplinary field and, as Executive Director of the Materials Research Society, he is keen to inspire people to engage with the wide range of world-class research in this area. He recently spoke to us at Research Features to discuss his organisation’s recent successes within materials science, before highlighting the direction he would like to see research go in the future.
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ome of the greatest landmarks across the world only exist because of materials science. Whether it be Sydney Harbour Bridge, the Eiffel Tower or a simple wine glass, materials science has shaped modern-day life as we know it. Behind each material is a story – a whole host of scientific work dedicated to establishing the structural and mechanical components of life’s building blocks. At the forefront of this work is the Materials Research Society (MRS), a non-profit Pennsylvania-based organisation which has been responsible for getting materials research seen and heard by the masses, through various TV shows, museum exhibits and interactive games. MRS’s philosophy is to advance materials research and, consequently, improve the quality of life of people around the world. Research Features recently spoke with its Executive Director, Dr Todd Osman, to discuss this further, and determine why materials science remains such an important area of research and development. Hi Todd! Thank you for speaking with us today. How would you describe your role as Executive Director of the Materials Research Society (MRS) and what kind of responsibilities do you have? Quite simply, I have three primary roles as Executive Director: 1) to facilitate the work of the society; 2) to infuse our mission, vision
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and values into all that we do; and 3) to ensure the long-term vibrancy and relevancy of the society. Could you tell us more about MRS’s background and the kind of work into materials science that you do there? Rustum Roy, one of MRS’s founding members, stated that 'in the very first meeting (1973) of the Materials Research Society, we stressed our hope that the MRS would become the international society in interdisciplinary materials research'. From our founding until today, we have focused on the field of materials research, engaging physicists, chemists and engineers alike. 48% of our members hail from outside of the United States, with 50% of attendees at a recent MRS Fall Meeting travelling internationally to convene with their peers. Whether it be our meetings, publications, or our numerous other programmes, we simply aim to fulfil our vision, 'providing a framework in which the materials disciplines can convene, collaborate, integrate and advocate'. MRS has members from academia, industry and government. How important is it to have worldwide collaborations with other research institutions, especially in terms of enhancing materials research and developing next generation devices? Connecting people and facilitating the cross-pollination of ideas locally and globally is at the heart of today’s research and development enterprise. In his book
NanoDays is a national week of community-based educational outreach events to raise public awareness of nanoscale science and engineering and its potential impact on the future Photo courtesy of the Materials Research Society Foundation
The Medici Effect, Frans Johansson defines innovation as occurring best when engaging diverse backgrounds, industries, cultures, and disciplines. Students travel abroad to study. Multinational corporations manage technological developments across continents with global and local partners. Research programmes are established between international institutions, leveraging expertise and unique equipment that each possesses. These global interactions and collaborations catalyse materials research,
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creating new ideas and approaches to meet local needs as well as global demand. What impact do you think MRS has had on materials science since its establishment? Are there any personal accomplishments you are particularly proud of? Let me start with a quote from an article written in celebration of the Society’s 40th anniversary: “MRS’s success is a story of the people who opened the doors to interdisciplinary inquiry and those who
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subsequently charted a path that led to remarkable research advances, professional partnerships, and public appreciation for the role of materials in our lives. These individuals – with their openness to and respect for new ideas and directions, entrepreneurial spirit, and commitment to excellence – created a very special and enduring MRS culture.” I’m not sure I could say it much better than that. MRS’s global, interdisciplinary focus was novel for a scientific society when we were founded, but definitely aligns with how materials
Materials have changed our history and continue to shape our future
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The Hagamos con-Ciencia outreach programme exposes 5th and 6th grade students in rural and/or impoverished areas of Mexico to the excitement of science and technology Photo courtesy of the Materials Research Society Foundation
Elastic deformation above 1% applied by “Feynman’s hands” at the nanoscale, which can lead to drastically different physical and chemical properties (symbolised by the colours) from the stress-free material Credit: Zhaohua Wang, Yan Liang, and Sina Moeini-Ardakani
research is conducted today. In the past 43 years, the world has become increasingly more interconnected and research increasingly more collaborative, spanning disciplines, institutions and continents. MRS was on the vanguard of those philosophies in 1973 and continues to explore, identify and respond to the evolving needs of our community. Does materials science research receive as much funding and recognition as it should? Materials are at the heart of every major technology, and there has been an increasing recognition that our critical societal challenges will require new materials and/ or advanced manufacturing techniques to more efficiently produce materials. These developments will increasingly require funding, support and investment, both from public and private sectors. Beyond funding,
and like all fields of science and engineering, there is a need to better communicate the importance of materials to the public and to the next generation of students. The Making Stuff television series (a fourpart PBS primetime series on materials science, coproduced by MRS and NOVA) and Strange Matter museum exhibits (an interactive travelling exhibit, developed by MRS in partnership with the National Science Foundation (NSF) and the Ontario Science Centre) aim to engage the public around the importance of materials and science. And our Impact of Materials on Society university course is designed to expand the social literacy of scientists and engineers, as well as the technical literacy of humanities and social science students, all by exploring how science, engineering and society are interrelated.
Connecting people and facilitating the cross-pollination of ideas locally and globally is at the heart of today’s research and development enterprise 8
Within MRS, you have the Materials Research Society Foundation. Could you tell us some more about what this is and why you decided to set it up? MRS’s mission calls for us to advance interdisciplinary materials research and technology to improve the quality of life. We founded the Materials Research Society Foundation in 2012 to build upon our tradition of public and STEM (science, technology, engineering, and mathematics) education outreach programmes and to better support our mission. Our Foundation seeks to leverage grants, donations and corporate sponsorships to serve the needs of the materials community, utilising the Foundation to accomplish more together than any one group can do alone. Through the Foundation, we have been able to increase the number of grants awarded to our members for outreach projects in their communities. We have expanded the Broadening Participation in Materials programmes to better engage underrepresented groups. Our Focus on Sustainability efforts have also grown dramatically, raising awareness of the nexus between materials, materials research, and sustainable practices. Why are grassroots initiatives and programmes, such as MRS University Chapters and the Strange Matter travelling museum exhibits, so important for enhancing materials research within the community?
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Thought Leadership
Dr Todd Osman
What impact have these initiatives had? Our education outreach programmes are important to catalyse the visibility, engagement and impact of science and technology. Our Strange Matter museum exhibitions have attracted over 5.3 million visitors in North America, Latin America, Asia and the Middle East. The Materials Research Society Foundation has supported Polycraft* to engage the next generation of science students via on-line gaming, and Hagamos con-Ciencia, for outreach to elementary school children in rural Mexico. Likewise, the Foundation has supported SciBridge, a programme connecting students in Africa to materials scientists in the United States, and Chemistry on Computers in Kenya, a project that develops computer-based materials chemistry curriculums for secondary school labs. The majority of our Foundation grants are proposed and conducted by MRS University Chapters. These students are passionate and talented and represent universities from around the world. For them, the benefits are twofold. They play a vital role in bringing research out of the laboratory and into classrooms and to the general public – raising interest in materials science and how it impacts our daily lives, and in turn, inspiring the next generation to consider STEM careers. At the same time, these projects help prepare our Chapter students for future
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professional and leadership roles in the materials community. In what direction would you like to see materials science research going over the next ten years and how will MRS’s research strategy play into this? The key global challenges of the 21st century – developing green energy and transportation, guaranteeing clean drinking water, engineering innovative biomedical devices, and advancing a new generation of computation and communication – all require materials solutions. We are fortunate that our membership includes women and men from more than 90 countries, and that they bring with them a rich and varied background of skills, knowledge and viewpoints. If we continue to honour the MRS mission and vision, then our role is to connect these people and their ideas, and draw on the wisdom that this diverse community can provide. Together, we will play a critical role not only in developing solutions to these key challenges, but also in communicating and disseminating these advancements to the global community. And of course, we’ll continue to advocate for sustainable funding of science, provide forums for public-policy discussion, support STEM education initiatives and play a significant role in developing and nurturing the next generation of materials scientists.
Materials have changed our history and continue to shape our future. We expect an exciting decade ahead and feel confident that MRS is well positioned to lead the way – advancing materials and improving the quality of life. * Polycraft is an educational technology which adds additional materials and tools to the basic Minecraft online game. The add-ons have a chemistry and engineering focus and behave in a scientifically accurate way.
Contact Materials Research Society 506 Keystone Drive Warrendale, PA 15086 USA E: info@mrs.org W: www.mrs.org www.facebook.com/materials.research. society https://twitter.com/Materials_MRS
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Materials
The REEMS Programme: discovering untapped talent To many, materials science represents a fairly inaccessible, complicated topic of science requiring a highly academic approach. Mr Bartlett Sheinberg’s Research Experiences and Exploration in Materials Science (REEMS) Programme aims to overcome this – contextualising materials science for community college students. The programme’s approach also aims to instil confidence in these students and provide them with skills to help them progress in their academic careers.
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aterials science is a topic involved in every facet of life. From the car you drive to work, to the clay on the white cliffs of Dover, materials are everywhere and have a significant impact on life as we know it. Understanding the extent of this impact is critical and should be accessible to whomever is interested, regardless of academic background or financial status. Delivering materials science to serious-minded students is vital not only for developing the next generation of materials scientists and engineers, but for generating a technically prepared workforce. The study of materials provides an academic umbrella under which community college students can appreciate concepts in the physical and biological sciences, engineering and computational science. An introduction to materials provides an important context for appreciating their coursework and generates an invaluable selfconfidence as they move forward to complete their undergraduate degree and transition to graduate school or into the technical
Dr Rafael Verduzco giving a tour of his lab to REEMS participants
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workforce. It is in this area that Houston Community College’s (HCC) Mr Bartlett Sheinberg, and his increasingly popular REEMS Programme, prevail. OPENING DOORS This programme – entitled Research Experiences and Exploration in Materials Science (REEMS) – is funded by the Division of Materials Research at the National Science Foundation (NSF) and is aimed at bridging the gap between community college and university for talented students at HCC who will be transferring primarily into engineering, the physical and biological sciences, and computational analysis. As Mr Sheinberg describes it himself: “The REEMS programme gives students an opportunity to see first-hand the broad scope of materials science. These experiences combine academic experience with recognition of the roles which materials can play in solving important societal issues and lay the foundation for the identification of interesting and meaningful
The REEMS programme gives students an opportunity to see first-hand the broad scope of materials science. Academic and career exploration is the key objective 11
Materials
career opportunities. Academic and career exploration really is the key objective of the REEMS programme. We provide the means for students to take the first steps towards exploring academic pathways and potential careers.” FINDING THAT SPECIAL SOMETHING Following the programme’s success since its inception in 2015, Mr Sheinberg’s role as mentor, ambassador and principal investigator has become ever more important in identifying ideal candidates. Each autumn, students are recruited and, through a highly competitive process, are selected for the following year's summer research experience. During the autumn semester an additional cohort of students is recruited to apply for entry into the seminar series "Impact of Materials on Society" (IMOS). Over the autumn semester, REEMS staff provide a series of seminars on university transfer opportunities, networking opportunities with materials professionals, and one-on-one transfer guidance. The REEMS programme welcomes students across all academic interests and majors. During the recruitment process, for either the summer research experiences or into the IMOS seminar, students' grades are an important indicator. However, their attitude towards their study and a demonstrated interest in discovery are critical selection criteria. “Many students come into my office and say, ‘I really want to do such-and-such’, and one of the things I’ve always tried to do is identify those students who possess that intangible gleam in their eye. One of the objectives of the REEMS programme is to quantify what that gleam in the eye means in terms of their future academic pursuits and their ability to appreciate the opportunities which the REEMS programme provides as they consider their futures.” THE IMPORTANCE OF DIVERSITY HCC is an open admission institution which provides students with a cost-effective education during their time at Houston Community College and supplies a second chance for those students to prove themselves academically, as well as the opportunity to
REEMS student Raymond McCoy presents his poster from the 2016 REU
enhance their maturity level, so that they can succeed in their upper division work. Community colleges, across the United States, are home to a highly diverse population of individuals from different nationalities, backgrounds and situations. Many of these students do not realise their own potential talent and abilities – REEMS provides that opportunity. Because of this, Mr Sheinberg offers an individual approach to interviewing each REEMS applicant to ensure that there will be a demonstrated mutual benefit for the student and opportunities provided by the programme. He said: “Applicants might have a great academic background and our selection of students is based upon why they want to become involved in the REEMS programme and what their expectations are from it. I like
The programme forced me to become a better, more vigorous student and, although I found it hard at first, I truly appreciate what it, and Dr Sheinberg, has done for me 12
to make sure that there is an overlap between what the programme can offer, and what the student hopes to take out of it. “At HCC, you have a population of roughly one third African-Americans, one third Hispanics and the final third made up of both Caucasians and Asians. Funding agencies, universities and employers are interested in looking at students who originate from diverse cultures, are highly motivated and have demonstrated a strong work ethic. REEMS plays a role in identifying these talented students.” For Dr Megan Robertson at the University of Houston, one of REEMS’ partner institutions, having this diversity is a real benefit. She said: “My university has a significant number of students who transfer from community colleges, so this is an important avenue for us. We have a lot of students who work while they’re at school, or maybe they’re the first person in the family to go to university – that sort of experience. “Having this diversity is a really nice aspect of being in such a multicultural city, as it can offer new perspectives to research – I think there
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REEMS students at the West Houston Center with staff members Dr Yibran Pereramercado and Dr Gizelle Davis – they are working on the scanning electron microscope, on loan for the REEMS Programme from JEOL, USA
are only advantages to having that level of diversity in the programme.” IMPACT OF MATERIALS ON SOCIETY During the spring term, the IMOS seminar provides a significant emphasis on contextualising and teaching students about the impacts of materials on society. This includes “broadening students’ horizons” in terms of how materials have shaped cultures, geo-politics and technology advances over the past three to four thousand years. Topics in this seminar series discuss the intersection of materials, technology, anthropology, economics and politics. Mr Sheinberg notes that IMOS plays an important role in helping students to realise their career path. He said: “As an example, IMOS begins by exploring the cultural aspects of clay and the impact of it on cultures, and the evolution of the material to include superconductive materials. It’s interesting to see how the transition changes student perceptions as we explore both technology, cultural developments and impacts.
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“One of the results of this seminar is that students start to ask themselves: if I want to have a career in science, engineering or even materials research, what impact can I have on society as an engineer or a scientist? How am I going to impact society? What problems can I solve? The identification of societal problems and challenges and a realisation of the importance of materials science in solving those challenges is one of the key objectives of the seminar series.” TEAMWORK MAKES THE DREAM WORK Mr Sheinberg also highlights the concept of teamwork as a key benefit from the programme, through the IMOS seminar series and preparation for the summer research experiences. “Students who participate in the REEMS programme have an opportunity to participate in teamwork. One of the objectives of the programme is to demonstrate the value of working and contributing to team activities. The structure of the IMOS seminars incorporates lectures and group presentations by REEMS students. These presentations are based upon contributions from each team
member, incorporating and articulating their results to fellow students, faculty and guests during the seminar and responding effectively to questions, on an individual basis and as a member of a team effort. These experiences are important for those REEMS students who participate in summer research and present their findings at the REEMS REU poster session at the end of each summer.” Mr Sheinberg noted that the REU experiences provide the first formal participation in team experiences for many of these students. They learn the importance of sharing results, seeking assistance from research staff and a realisation of their respective individual roles in addressing research challenges. The REEMS programme is unique among conventional REU activities. REUs are generally sponsored by research universities and recruit lower and upper division students, often from community colleges. Students participating in the REEMS REU are recruited and placed in university research projects by REEMS staff, in close collaboration with research faculty. REEMS has established partnerships with regional universities and faculty from
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the University of Houston, Rice University and the University of Texas Health Science Center – Houston. In 2016 twelve students participated in the REEMS REU and in 2017, with the addition of a new faculty member at Rice University, fourteen students will be participating in the REEMS REU. IDENTIFYING TALENT Mr Sheinberg describes how almost all REEMS REU students finish their summer research experiences with a high level of self-confidence, and the realisation that they have both academic potential and the talent to consider new and challenging academic and career pathways. The increase in confidence, tied with the realisation of their talent, are strongly influenced by each of the seven research faculty during their summer experiences. One of the objectives of the REEMS programme is to provide each student with the ability to determine their own academic and career futures. This self-confidence is something Zeshan Rizvi, a member of the 2016 REEMS REU and the forthcoming 2017 REEMS REU, has experienced. He said: “When I first started the programme, I wasn’t too sure exactly what I would get out of it – it seemed a little too good to be true, but it turned out to be the real deal. Initially, I found it a bit overwhelming with the duties and responsibility given to you. I also found it hard to get used to the workload and the vigorous routine of being part of a research programme and a research group, but eventually I learned to really enjoy it. “For me, the experience I gained just from being a part of the research group, learning about what they do on the front lines of research on a daily basis, was the most important thing. The IMOS seminar and REU forced me to become a better, more vigorous student and, although I found it hard at first, I truly appreciate what it has done for me.” MAKING UNIVERSITY ACCESSIBLE Another former REEMS student, Raymond McCoy, even said that without the programme, he would never have even considered going to university – seeing a life in the workforce for himself instead.
He said: “I wasn’t planning on going any further than my associate degree, but the programme sets you up with some great university contacts. It really amplifies the opportunities you receive going into the next stage of your academic career, and it sets you up with skills that make you distinct from other candidates going for jobs, positions, internships – whatever it may be.” However, Dr Robertson believes the programme does not only benefit the REEMS students themselves, but her lab as well. In fact, she was so impressed by the quality of the students she mentored last year, that she decided to keep them on. She said: “The students I had last year were excellent and I managed to find a way to continue their work in my lab even after the summer programme was done. After all, the REEMS programme doesn’t just provide an opportunity for them, it provides an opportunity for us as well. In the end, we could continue the work they had done over the summer, and we’re even going to get a research publication out of their work.” FUTURE PLANNING Mr Sheinberg looks forward to other
Mr Sheinberg is like a father to us – you cannot put a price on what he has done for me. No one will help me in the same way he did 14
community colleges and university partnerships emulating part of the REEMS programme. Part of his job is to work with interested community college and university partnerships to discuss funding and structural and programmatic aspects which are unique to each partnership. Mr Sheinberg mentioned that while he and his staff play an important role in administration of the programme, one of the critical components of the programme are the multi-faceted roles which each of the REEMS research faculty play in the process. He said: “What has made it successful are the research faculty members. These are the people who really inspire the students – the linchpins that make this thing work. Students get a chance to meet with them, work in their labs, and it’s sort of a double-edged sword in a way – on the one hand, the students feel a little bit intimidated, but on the other, they get to say, ‘wow, this is really interesting’ and eventually, ‘I can do this’.” MR BARTLETT SHEINBERG: MENTOR Gelareh Nobakht, a current REEMS student, somewhat disagrees with Mr Sheinberg's characterisation of his role, stating that Mr Sheinberg’s tenacious energy and fatherly care for students is the reason the programme has proved so successful over the years. She said: “He’s like a father to us. He’s the one who encouraged me to go to university and he has a lot of hope for me, and all his students. He provided recommendations for me, he focused me on universities that would be right for me – you cannot put a price on what he has
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Detail RESEARCH OBJECTIVES Mr Sheinberg’s current research objectives focus on identifying, educating and serving as the Principal Investigator for students involved in Houston Community College’s REEMS programme.
Above: Mr Bartlett Sheinberg, leader of the REEMS Programme Left: Dr Megan Robertson's research group and REEMS students
done for me in the past two years. No one will help me in the same way he did.”
It forces them to think about it and it makes them much better teachers in the future.”
Sogol Gharaeimoghadam, another current REEMS student, can also vouch for Mr Sheinberg’s fatherly persona, stating that his “really friendly personality … [and] helpful approach throughout the programme” had made it a “blessing getting to know him”.
Dr Rafael Verduzco of Rice University agreed as well, stating: “The REEMS programme helps me and my graduate students in that it actually forces us to explain our science in a way that makes sense to somebody who isn’t an expert in the field, because we are explaining it to people who are completely new to the topic. It is always helpful for us to learn how to do that more generally and more broadly.”
Similarly, Dr Zachary Cordero, the new research faculty mentor for two additional REEMS students at Rice University, agrees that the programme’s success is down to Mr Sheinberg, predominantly due to his ability to identify and place candidates. He said: “I think credit is due to Bartlett (Mr Sheinberg) for attracting good students and for trying to put them on placements that he thinks are appropriate to them and their personalities. I specifically requested students who have an interest in tinkering, working with their hands, and have a natural proclivity for doing experiments, and Bartlett tried to connect me with students who aligned with those criteria. The programme has been successful mainly due to him.” ADDITIONAL BENEFITS For Professor James Meen, the programme has been a positive not only for the REEMS students that he mentors, but also for the graduate and postdoctoral students he oversees at the University of Houston. He said: “It is a positive for the graduate students especially, because they have to explain to somebody with a limited amount of background what they’re doing in the lab.
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REACHING OTHERS In addition to his responsibility administering REEMS, and providing stewardship of existing West Houston collaborations and programmes, he is continually seeking new partnerships with community colleges, universities, professional societies and businesses to participate in a wide array of programmes focused on materials science education. Mr Sheinberg serves as the lead for the 2017 Materials Research Society Educational Symposium at the MRS autumn meeting that will focus on strategies for community college and university partnerships to develop lower division materials science educational programmes. For information on attending or submitting a presentation abstract: http://www.mrs.org/ fall2017/call-for-papers?code=BI1 If you would like to view the students' research posters or the abstracts from their projects, please contact Mr Sheinberg who will be happy to forward them to you.
FUNDING The REEMS project acknowledges financial support from the National Science Foundation, Division of Materials Research (Award 1460564) and additional financial support from the Houston Community College District Office. COLLABORATORS Professional Societies: • Materials Research Society Research Faculty Collaborations: • University of Houston: Dr Jakoah Brgoch; Dr James Meen; Dr Megan Robertson • Rice University: Dr Zachary Cordero; Dr Margaret Cheung; Dr Rafael Verduzco • University of Texas Health Science Center – Houston: Dr Laura Smith Callahan BIO Mr Bartlett Sheinberg is the founding Director at the West Houston Center for Science and Engineering at Houston Community College which was established in 2006. He has served as a physics and engineering faculty member, and several administrative positions at Houston Community College for over thirty years. He currently serves as the Principal Investigator on Houston Community College’s REEMS programme. CONTACT Bartlett M. Sheinberg Director West Houston Center for Science and Engineering Houston Community College 2811 Hayes Road MC 1524 Houston, TX 77082 USA T: +1 (713) 718 5617 (Direct Line) +1 (713) 569 4046 (Mobile Number) F: +1 (713) 718 6884 E: bart.sheinberg@hccs.edu W: www.hccs.edu/whc
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Failure under complex strains and stresses: fracture and fatigue in advanced materials Professor Filippo Berto, at the Norwegian University of Science and Technology (NTNU), has been investigating a novel method of obtaining fatigue data from advanced engineering materials. Using complex techniques which allow for examination of multiaxial loading and high temperatures, his data show promising advances in the analysis of stress testing data which will have significant impact on component design and industrial applications.
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ithin materials science, as is true of anything, it is important to push the limits. This is especially important when researching material fatigue. In simple terms, this focuses on understanding how much stress a material can withstand before fracturing, through repeated stress cycles under controlled levels of intensity. THE NAME OF THE GAME Professor Filippo Berto is an experienced researcher within the field of materials science. Having achieved the highest honour possible in his first degree from the University of Padua, Italy (one of the oldest universities in the world and consistently highly ranked), he moved to Florence to complete his PhD in mechanical design. His return to Padua was inevitable, however, as was his rapid rise from researcher to assistant professor of mechanical design and then associate professor of mechanics. Clearly a rising star in mechanical engineering, he was most recently offered the Chair of Mechanics and Materials at NTNU’s Department
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of Engineering Design and Materials, in recognition of his academic achievements and prolific publication portfolio. Following exhaustive searches of the literature, Prof Berto identified key areas where fatigue data was lacking for modern engineering materials. When considering high-performance materials, high strength in high-temperature conditions is of paramount importance. Most researchers studying this area have focused on creep and low-cycle fatigue (deformation of a material and relatively low number of straining events respectively). However, because of the nature of the applications, high-cycle fatigue is a more likely real-world scenario. APPLYING THE STRESS To address this dearth of data on highcycle, high-temperature fatigue in advanced engineering materials, some researchers have suggested extrapolating current room temperature data where this is shown to be experimentally possible. This led Prof Berto to examine whether Strain Energy Density (SED), an assessment which has previously
Materials Science
Superalloys in turbine engines are used at 90% of their melting temperature. Therefore, being able to accurately predict how these materials behave is of paramount importance 17
Materials Science a
b
a b Top and Above: Geometry of un-notched and V-notched specimens (a) and details of the notch tip (b)
been shown to be applicable to room temperature data, could be extended to high temperature material fatigue. The concept is that strain data for a material can be expressed as a function of volume to give values which hold true irrespective of the specimen’s geometry. Using samples of advanced engineering materials called superalloys (such as DZ125 and Inconel 718) which are designed to be used in high temperature environments such as turbine engines, as well as high grade carbon steel and advanced titanium alloys, the team tested their fatigue at high temperature to confirm that the SED data held true. Using a combination of hourglass-shaped specimens and those which had either blunt or v-shaped notches to simulate machined components, the team subjected them to both high temperatures and cycles of increasing tensile stress to the point of failure. For the work with titanium they also included torsional stress and multiaxial loading protocols to investigate whether these resulted in diverse SED profiles. CRACKING OPEN THE DATA The fatigue data was analysed using
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Above: Fracture surface of plain specimen tested at 650°C (a) (Δσ=140 MPa, N=284049), and room temperature (b) (Δσ=900, N=155000)
Above: Comparison between the fracture surface of plain specimen tested at 650°C (a) (Δσ=140 MPa, N=284049) and room temperature (b) (Δσ=900, N=155000), with the same magnification value
standard models and specific mechanical loading equations to compare how the different samples responded to the stresses applied. This allowed for the calculation of the SED which can then be plotted against the number of load cycles. This clearly demonstrates the power of the SED approach as all data points fall within a narrow band on the scatter plot. From these data, the failure energy of each material can be calculated independently of its geometry.
(returns to original shape) or plastic (bends without breaking) deformation.
It also clearly showed that the approach is extendable across the range of operating temperatures for which the material is designed. Linear relationships at room temperature can also be applied to high temperature situations, as long as certain conditions are met. Examples of these conditions include remaining within elastic
STRETCHING THE REACH The same holds true, to some extent, for Prof Berto’s work with titanium alloys. By applying different control volumes to torsional over tensile loading, the data can again be algebraically manipulated to provide comparable values for SED under conditions for torsional, tensile and multiaxial loading. This makes it possible for these varied conditions, for both notched and un-notched samples, to be simply evaluated. This synthesis of all the fatigue strength data, regardless of loading mode or specimen geometry, displays the unifying nature of the SED approach.
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Detail What benefits, in terms of academic and collaborative opportunities, are available to you as Chair of Mechanics and Materials at NTNU? It is like driving a Ferrari instead of driving an ordinary car. You have visibility and many contacts around the world with very good feedback on your scientific work. You have the opportunity to connect with all the most prestigious universities around the world: ETH, Harvard Berkeley, Stanford and Caltech.
How can SED be most simply explained to someone unable to follow the complex algebraic equations used to describe these processes? SED is the local energy necessary to generate damage to the material.
What led you to investigate SED as an approach to unify stress data in advanced engineering materials? I wanted to find a general simple method for fatigue and fracture design. Energy is the basis of all the most important physical concepts.
What more needs to be done to extend the field of high temperature fatigue in the high cycle regime? New experimental tests at different temperature ranges are needed, and a greater understanding of the main phenomena related to crack propagation at high temperature.
How do you see SED being used in ‘real world’ applications? Many industries have understood the potential of SED and its versatility to solve complex problems in a simple way.
RESEARCH OBJECTIVES Dr Filippo Berto’s research primarily focuses on the brittle failure of different materials, the mechanical behaviour of metallic materials, the fatigue performance of notched components, and the reliability of welded, bolted and bonded joints. His recent research has looked to further assess the ‘Structural Integrity’ discipline, by analysing the fatigue characteristics of particular materials commonly used within engineering. COLLABORATORS Dr Pasquale Gallo (Kyoto University); Dr Alberto Campagnolo (University of Padua); Dr Marco Colussi, Cimolai; Dr Filippo Abbatinali, Cimolai; Dr Javad Razavi NTNU, Trondheim; Dr Alberto Lorenzon, Cimolai; Dr Marco Grotto, Officine Meccaniche Zanetti; Dr Thomas Borsato, VDP fonderie; Dr Steffen Sunde, NTNU Industries: Cimolai; Officine Meccaniche Zanetti; Zincherie Valbrenta BIO
FROM MAN TO MACHINING It is this ability to collapse the data into a narrow band curve that makes the SED approach preferable over current methods. The more common practice of presenting the data in terms of the stress range is unable to collapse the data into such a convenient format. For industrial applications, this is an important advance over current methodologies. As many components are continuously refined and redesigned, having a parameter for mechanical resistance which is not dependent on the geometrical shape means that testing the component every time is no longer necessary. This will save considerable time and money, and will also offer great potential within the advanced engineering materials sector. When considering the sectors in which these materials are applied, such as the
manufacture of turbine engines for aerospace and marine markets, or the further processing of metals in hot rolling and machining procedures, it is no wonder that advances such as these are required. Superalloys in turbine engines are used at 90% of their melting temperature, as the thermodynamic efficiency of these engines increases with increasing turbine inlet temperature. Therefore, being able to accurately predict how these materials will behave is of paramount importance. As these technologies progress, the tools required to design and manufacture them also need to progress at a similar rate. Prof Berto and his team are leading the way in improving the understanding of materials science, as well as providing advantageous solutions applicable to those working within the industry.
The ability to collapse data into a narrow band curve makes the Strain Energy Density approach preferable over current methods www.researchfeatures.com
Dr Filippo Berto received his degree in Management Engineering in 2003 from the University of Padua (Italy). Following this, he attended a PhD course at the University of Florence before returning to the University of Padua to work as a researcher. While there, he had many roles including both the Assistant Professor of Machine Design and the Associate Professor of Mechanics. His most recent role is one of the most prestigious available at the Norwegian University of Science and Technology, where he currently works as the internationally renowned Chair of Mechanics of Materials. CONTACT Filippo Berto Department of Engineering Design and Materials NTNU Richard Birkelandsvei 2B 7491 Trondheim Norway T: +47 7359 3831 E: filippo.berto@ntnu.no W: www.ntnu.no/ansatte/filippo.berto /filippo.berto.9
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Morphing of a NiTi textile subjected to radiation heating
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Physics
Functional textiles driven by transforming NiTi wires Weaving textiles from nickel-titanium (NiTi) wires offers a way to give garments a ‘shape memory’ where they can return to their original shape after being deformed by applying heat. Dr Ludek Heller and Dr Peter Sittner, at the Institute of Physics of the Czech Academy of Sciences, have found new ways to make and process wires to take advantage of the numerous, exciting applications of their NiTi wire technology, including in the manufacture of protective clothing for firefighters and astronauts.
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magine a dress that, no matter how much you crumpled it up or wrinkled it, could pop back to its original shape, just with a little heat. Imagine clothing that could move and morph designs, just by changing the temperature of the environment. All of this can now be achieved in the era of ‘smart’ or ‘technical’ textiles, where new technologies are being combined with traditional textile manufacturing to create high performance materials with a whole variety of exciting applications. It is not just high fashion and design that has been making use of the rapid development of technical textiles. Sportswear manufacturers are very interested in novel textiles that help better regulate body heat, or offer better protection in extreme weather conditions. These applications are not just limited to clothing either – technical textiles can now be found in bandages that have enhanced antibacterial properties to reduce the probability of post-operative infections. Among these, one of the most exciting developments is the use of shape memory alloys in technical textiles. These are materials that can be set into a shape and, no matter how they are distorted, they will return to their original shape on heating. This is how ‘animated’ dresses can be created that seem to move of their own free will. Dr Ludek Heller and Dr Peter Sittner, at the Fyzikální ústav AV ČR, are experts in this highly interdisciplinary area. Their research is about finding new ways to combine nickel-titanium
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wires with traditional textiles to achieve many of the proposed novel applications. Dr Sittner describes their role as being, “physicists – metallurgists – mechanical engineers, that, coupled with textile manufacturers, make hybrid metallic textiles”. PROPERTIES OF NITI Why is NiTi the alloy of choice for making the wires that are combined with traditional yarns? NiTi (sometimes called NiTiNOL, an acronym derived from its composition and place of discovery – Naval Ordnance Laboratory) is the most commercially successful shape memory alloy. NiTi wires and thin filaments have functional and structural properties outperforming other shape memory alloys. NiTi is relatively easy to process into wires that range in diameter from a few to tens of microns thick – roughly the thickness of a human hair. They can be combined with traditional yarns made from cotton or wool to make a variety of different fabric types. The stretchability of the NiTi wires (due to their superelastic functional property) is fairly similar to the blended yarns so the overall fabric is suitable for use in items like clothing.
It is the superelasticity and shape memory properties of NiTi that Dr Heller and Dr Sittner are most excited about. Much of their work has been on characterising the thermomechanically induced martensitic transformations that give the NiTi wires their unique physical properties, and on finding new ways to transform these properties into smart and functional properties of NiTi textiles. Martensitic transformations involve the movement of atoms within the material in such a way that the crystal structure is changed. There are technological issues arising from incompatibilities between NiTi wires and textile yarns (such as temperature resistance, friction coefficient, bending stiffness) that had to be overcome. For example, the low friction of the wires has made it challenging to make stable fabrics, as the warp and weft threads slide over each other, meaning the fabric distorts with handling and wear. By using a traditional weaving technique called leno, where the warp yarns are twisted around the weft, they have successfully created stable woven fabrics. MARTENSITIC TRANSFORMATIONS All exciting properties of NiTi stem from the reversible solid state martensitic transformation that takes place in the material when temperature and stresses are properly changed. The word reversible is of key importance here as martensitic transformations are common to other materials such as steels. In steels, however, when a crystal lattice of the parent (austenite) phase transforms into a different crystal lattice of the lower symmetry phase, the reversibility is lost because of the dislocation slip at the interface and lattice volume changes introducing defects and internal stresses. The way back for the atoms to the initial sites of the parent phase is thus lost and therefore there is no shape memory effect. In contrast, when NiTi transforms to the product martensitic phase, the atoms never lose their way back even after extensive complex deformation, since the accompanying plasticity is marginal and the interface remains highly mobile. In these exciting alloys, the transformation proceeds smoothly in
Imagine clothing that could move and morph designs, just by changing the temperature of the environment. This can now be achieved in the era of ‘smart’ or ‘technical’ textiles using NiTi wire technology 21
Physics
Figure 1: High energy synchrotron x-ray diffraction helps to detect accummulation of residual stress and residual martensite upon superelastic cycling of thin NiTi filaments due to concurrent martensitic transformation and plastic deformation by slip
Figure 2: Reversible straightening of a single knit loop made from a 100 um NiTi wire subjected to tensile loading. The straightening is accommodated via a solid state transformation of the initial austenite phase. This deformation mechanism was tracked using microdiffraction tomography revealing the spatial distribution of martensite and R-phase induced by bending dominated loading
response to stress and temperature variation with negligible lattice volume changes but high lattice distortions giving rise to highly reversible strains (up to 10%). In addition, the product martensite phase can easily deform through cooperative translation gliding of entire planes of atoms (twinning) giving the martensite so-called pseudoplastic behaviour. But again, pseudoplastically displaced atoms of martensite will find their way back to the initial sites of the parent austenite phase by heating. This is where the memory of shape comes from. Although the martensitic transformation in NiTi alloys is theoretically perfectly reversible, when NiTi wires are loaded cyclically they
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gradually get longer – a sign of irreversible processes. That irreversible processes proceed in cyclically loaded NiTi wires was shown by recent in situ x-ray diffraction studies led by Dr Sittner (Figure 1). The irreversible processes are of particular concern for fatigue performance of NiTi wires and are currently the focus of Dr Heller’s team. Better understanding of the mechanisms leading to premature fatigue is key to further applied use of NiTi alloys. MANIPULATING MARTENSITIC TRANSFORMATIONS IN NITI When fine NiTi wires arrive from production by cold drawing they behave elastically just like stainless steel wires. This is because the
microstructure is heavily deformed with a high density of crystal defects preventing shape memory functionality. Therefore, microstructure recovery by heat treatment must be done to restore them. Ten years ago, Dr Pilch from Dr Heller’s research team developed a unique method of thermal treatment using short electric current pulses. The method allows a wide range of desired microstructures and properties to be set to NiTi wires. Functional properties of NiTi wires can be customised for a given application, particularly to elastic modulus, reversible strain, ductility, strength etc. This method has been extended to continuous annealing where the thin filaments are being respooled from one spool to the other while being annealed (heated then slowly cooled), which is of particular interest for textile applications. SHAPE SETTING OF NITI TEXTILES Imagine textiles that look like a normal fabric but have shape memory properties. For this, textile processing combining both the NiTi wires and common yarns has been successfully tested. Applying the heat treatment while the textile is constrained in a desired shape allows researchers not only to induce shape memory properties in NiTi but also to shapeset NiTi wires creating the shape of the entire fabric (see main image). This process of the constrained heat treatment of NiTi wires is called shape setting. The complex internal architecture of NiTi textiles is created partially by weaving (knitting) and partially by the shape setting treatment. In addition, the macroscopic shape of the 2D textile can be set as well. The key issue when shape setting hybrid NiTi textiles is to heat treat the NiTi wires while protecting the surrounding heatsensitive yarns. Shape setting at moderate temperatures is the only way to achieve that. Dr Heller and Dr Sittner’s research team has been exploring how to shape-set NiTi wires at temperatures as low as 250°C, employing the stresses arising naturally in NiTi wires from the reverse martensitic transformation driven by the supplied heat. Shape-set NiTi wires embedded in textiles have wavy geometry due to their interlacing with the textile patterns. This wavy geometry allows for large deflections due to wire bending. This deformation mechanism is further assisted by martensitic transformations, which in this case proceed in more complex ways than straight wires being simply stretched. Dr Heller's team systematically makes use of diffraction techniques to track in situ martensitic transformations in NiTi wires undergoing thermomechanical loadings. To
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What are the properties that make NiTi wires so special? Of course the most fascinating property is the memory of shape upon heating. It has been transferred from 1D to 2D by textile technologies. From the mechanics point of view the most striking is that a NiTi wire can behave plastically so that it remains in any shape given to it yet at just a slightly higher temperature it becomes stiffer and highly elastic – the original shape is restored upon unloading. One can switch between both material states by changing temperature. When stretching NiTi wire in the superelastic state one can feel and even hear how the phase transition proceeds in the material giving rise to ~5% of deformation that is induced suddenly when reaching a critical stretching force. All unique properties of SMAs derive from the martensitic phase transformation in solid state – diffusionless rearrangements of atoms within the material. Among SMAs, NiTi are unique in the ability to undergo large recoverable strains up to 10% and are commercially by far most successful. NiTi wires can reversibly change the stiffness, recover strains, and exert tensile stresses hundreds of MPa by changing temperature by a few tens of degree Celsius within the range from -50°C up to 100°C. All these properties may be utilised in NiTi wires that can be easily shape set into any tortuous shape. What inspired the idea of using NiTi wires in textile applications? Actually, when you touch a fine NiTi wire this idea comes naturally. The fine NiTi wires possess the magic shape memory properties and are even stronger than bars or thick wires. So why not combine multiple thin wires using textile processing technologies to make superelastic cables or textiles with memory of shape or roughness? Indeed, by setting a densely wrinkled shape on a flat textile, it will remember its surface roughness, etc. From another perspective, textile internal architecture can be modified by shape setting. A variety of textile patterns may be advantageously introduced into already woven or knitted textiles to improve or modify their properties. But
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we must note that NiTi textiles have already been used in the form of braided NiTi stents when we started this research 13 years ago within the frame of the large-scale European project, AVALON. How do you decide which types of textile processing are likely to give you the behaviour you want from the NiTi wires? Requirements of the textile to be engineered dictate the choice of the type of NiTi wires, textile pattern, shape setting, and textile processing. This makes the design of each end product rather complex as there are many variables to play with, and one variable may condition the other. For example, if large stretchability beyond the limits of NiTi wires is required then one has to go for suitable knitted patterns that allow for enlarged stretchability. But in knitted patterns NiTi wires are loaded in bending, giving the textile compliant mechanical characteristics that are very different from woven structures with two perpendicular sets of nearly straight wires that are much stiffer in plane deformation, reproducing the tensile properties of NiTi wires. Another example, when a 3D shape is required, shape setting is advantageous as it can replace time-consuming 3D textileprocessing methods – one can start from a flat pattern and extend it into 3D using shape setting. The shape setting has a side effect – it releases all deformation energy stored in wires when they are being interlaced into textile patterns. It is positive for knitted patterns that, thanks to it, are not prone to unravelling. Do you think it will ever be commercially viable for NiTi textiles to become commonplace? Because thin NiTi wires are rather expensive,
need special treatments, and are not fully compatible to common yarns, one cannot expect wide scale application – for example, in apparel or geotextiles. I think the use of NITi filaments in textiles is justified only in cases where they provide textiles with unique properties that cannot be achieved otherwise and these novel functional materials can be applied in a manner which justifies the money spent. In other words, for the time being only high-added-value NiTi textiles have a chance on the market e.g., in medical devices or special products. Our experience is that even if we demonstrate attractive functionalities of NiTi textiles, commercialisation of the end product is very difficult. On the other hand, as there are no other materials showing such a combination of structural and functional properties, there are no competitors… Which of the potential applications of these NiTi textiles do you think will be most exciting? Applications where we utilise both the shape memory properties and the ability to be shape-set. 3D-shaped textiles such as spacer fabrics being able to sense temperature and repeatedly react upon that by a change in stiffness and shape even against external pressure. I think no other material can equal NiTi textile in providing this combination of properties. For example, a compliant low profile patch of NiTi textile embedded in thermally protective clothes becomes larger, stiffer, increasing the space between the extreme heat and human body in a fraction of a second because NiTi senses the temperature and reacts immediately.
Dr Heller and Dr Sittner look at ‘shape memory’ alloys. These are materials that can be set into a desired shape, and no matter how they are distorted up to limits given by the nature of martensitic phase transformation, they will return to their original shape on heating
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Physics
Detail RESEARCH OBJECTIVES Dr Heller and Professor Sittner’s research analyses textiles and materials using thin NiTi wires. Through their wire technology, they aim to revolutionise not only the textiles industry but the medical industry as well. FUNDING • Avalon (www.avalon-eu.org) – European Commission Community Research 6th Framework Programme • NiTitex – Project funded by the Czech research foundation under project no. P108/10/1296
Figure 3: Prototype of a temperature-responsive 3D NiTi spacer fabric with the ability to reversibly increase and decrease its profile height and volume upon heating and cooling while being loaded by external pressure as illustrated in graph a). At lower temperatures the spacer fabric becomes compliant, deforming under pressure into a low profile thickness cold shape while becoming stiffer, thus forming a high profile thickness hot shape at higher temperatures. The 3D spacer fabric is based on a flat hollow knitted textile pattern that is 3D shape set as seen in b).
this end, synchrotron X-ray microdiffraction was used to identify martensitically transformed zones within a wavy 100 micron NiTi wire while being stretched, mimicking the NiTi wire loading in weft knitted NiTi textiles (Figure 2). NITI TEXTILES Embedding NiTi wires into textiles enables the engineering of a complex 3D structure thanks to the shape setting. Such NiTi structures can repeatedly undergo large strains thanks to both NiTi atoms shuffling back and forth, and wavy geometry of NiTi wires allowing for large deflections. These NiTi structures may be extremely compliant and soft at one temperature while becoming stiff and hard upon being heated by just a few degrees. The key for the successful design of NiTi textiles is to interlace NiTi wires into smart patterns. A collaborating textile engineer K. Janouchova, together with Dr Heller and Dr Sittner, has been working on designing lightweight, hollow 3D textiles using a unique weft knitting pattern. This forms a temperature-responsive spacer fabric that can triple its profile thickness when the temperature is changed by 30°C or lift up to 2000x its own weight. One application for this smart spacer fabric is as thermally protective cloth (Figure 3). FUTURE CHALLENGES The research group has already been awarded several patents for their work, including one for a low-profile stent graft (used to repair damaged blood vessels). The extreme thinness of the stent graft means the diameter of the delivery system catheter can be
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COLLABORATORS • Technical University of Liberec (www. tul.cz) • ELLA-CS (www.ellacs.eu) – Producer of health care devices • D'Appolonia (www.dappolonia.it) – Provider of engineering services
decreased. The graft is made from a unique woven textile incorporating 30 microns of NiTi wires combined with medical grade yarns that are low temperature shape-set into a tubular textile. Another patent is for developing a Velcro-like fastener that is made from an array of NiTi ‘hooks’ which open and close silently. This fastener is also immune to dirt and oil that can clog conventional Velcro fasteners stopping them from working. At present, NiTi use has mostly been restricted to medical, aerospace and automotive applications due to the costs associated with manufacturing. Shape-settable hybrid NiTi textiles offer a wide range of new applications, for example in medical devices or wearable electronics. Key technologies have already been developed for textiles made from superelastic filaments. The work of Dr Heller and Dr Sittner represents a major breakthrough in NiTi textile production from drawn filaments with subsequent heat treatment for simultaneous adjustment of the functionality, textile architecture and shape. Incorporating NiTi wires into textiles on an industrial scale, however, still poses challenges due to the additional machinery wear and friction from working with the metallic alloys during textile production. However, given the exciting applications, NiTi textiles will become ever more attractive as time goes on.
BIO Dr Ludek Heller's academic background has largely focused on mechanical engineering, having studied in both the Czech Republic and France. Dr Petr Sittner, after receiving his PhD in Solid State Physics from the Faculty of Mathematics and Physics Charles University in Prague, has made a long and distinguished career in the field of martensitic transformation and shape memory alloys. Together, they currently lead the SMA research at the Institute of Physics ASCR. CONTACT Dr Ludek Heller & Dr Petr Sittner Fyzikální ústav AV ČR, v. v. i. Na Slovance 1999/2 182 21 Prague 8 Czech Republic E: heller@fzu.cz (Ludek Heller) E: sittner@fzu.cz (Petr Sittner) W: http://ofm.fzu.cz/about-fmc http://www.fzu.cz/
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Understanding glassy dynamics
Physics
Dr Nussinov and Dr Kelton are professors at Washington University in Saint Louis. Dr Weingartner recently completed his PhD studies in Dr Nussinov’s group. A shared passion of these three researchers concerns the nature of one of the most common states of matter – glass. A deeper theoretical understanding of glasses may, in turn, lead to numerous applications. Apart from improving age-old studied silicate glasses (such as those used in windows), an understanding of the structure and dynamics of glasses might also have profound ramifications to the many varied and far more recently discovered glass formers currently appearing across diverse arenas. These applications include those of bioactive materials, new drug design (organic glasses are more soluble than crystals), and various industries.
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ne of the most interesting, yet challenging issues in physics is the enigmatic behaviour of glasses. These complex systems can be contrasted with the far better understood ordered crystals. Glasses are rigid. However, unlike crystals, glasses are not neatly ordered.
quantum mechanics comes to life on the very large spatial scale of the entire crystal; the well known quantum energy levels of electrons in single atoms lead to an analogous “band structure” in crystals. Indeed, the invention of solar cells and the transistor was made possible by the understanding of these precise band structures.
The periodic, ordered structures of crystals have long captivated scientists. In the 17th century, long before the discovery of the atom, prominent scientists such as Robert Hooke (an astronomer, physicist and first biologist to coin the term “cell”), Christiaan Huygens (a mathematician, physicist, and inventor of the first reliable pendulum clock) and their contemporaries proposed that the sharp facets of single crystals resulted from recurrent fundamental unit cell configurations. Indeed, as we now know, in simple crystals, the structure of extremely small atomic unit cells is replicated to span the entire system. In essence, this replication endows large crystals with quantum mechanical behaviours.
Inspired by these and other well known successes, Dr Nussinov initially proposed that (like crystals) the behaviours of glass formers might also be more readily understood within a quantum mechanical framework and provided a prediction for their viscosity. An intense pursuit followed in which the combined theory-experiment team of the three researchers and their collaborators examined the viscosities of all known glass formers and, to their delight, found that these conform to the theory's predictions. Additional aspects and new related ideas were introduced and critically studied by the team (many of which are detailed at length in Dr Weingartner’s recent PhD thesis).
Traditionally, quantum mechanics describes very small spatial scales (e.g., single atoms and molecules). However, thanks to the periodic locations of atoms in a crystal,
WHAT, PRECISELY, ARE SUPERCOOLED LIQUIDS AND GLASSES? In principle, and provided that they are sufficiently rapidly cooled (so-called
Understanding the nature of glassy dynamics is one of the few remaining unsolved and challenging issues in condensed matter physics, thus demonstrating the importance of the team’s research www.researchfeatures.com
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Physics
“supercooled”) below their melting point (temperature), all liquids in nature will form glasses owing to the fact that there is insufficient time for them to crystallise, and thus they will not form an ordered solid. Pure bottled water may also be supercooled in household freezers, allowing for interesting stunts (such as crystallisation into a column of ice upon tapping or pouring onto a hard surface). The viscosity of some supercooled liquids (i.e., their resistance to flow) can increase by fifteen orders of magnitude for just a modest temperature drop. Once a supercooled liquid has become sufficiently viscous at low enough temperatures, flow ceases and it behaves as an amorphous rigid solid – a “glass”. UNIVERSAL GLASSY DYNAMICS Understanding the nature of glassy dynamics is one of the few remaining unsolved and challenging issues in condensed matter physics, thus demonstrating the importance of the team’s research. In fact, to highlight the emphasis put on this subject by the scientific community, Philip Anderson, who was awarded a Nobel Prize in Physics (1977), described glassy dynamics and glass transition as “the deepest and most interesting unsolved problem in solid state theory”.
Over the decades, there have been numerous attempts to rationalise the behaviours of glasses. Usually these approaches appeal to various special parameters and putative temperatures. It has been a long held belief that (apart from their appearance in “reduced glass temperature” ratios) the standard equilibrium melting transition temperatures play no direct role in the formation of glasses.
The figure above demonstrates the collapse of all measured viscosities of known supercooled liquids onto a universal curve. The solid “General Curve” is the prediction of the theory; all other points are given by experiments. The logarithmic scale of the vertical axis corresponds to the ratio of the viscosity η of each supercooled liquid at a temperature Τ divided by the viscosity of that supercooled fluid at its equilibrium melting temperature Τmelt; note that this ratio varies by a factor of ~ 1016 (i.e., ten million billion or ten quadrillion) over the entire range – the viscosity of the glass can be far larger than of the supercooled fluid at its equilibrium melting temperature. The dimensionless constant B ~ 0.1 does not vary significantly from fluid to fluid. Similar behaviour appears for the relaxation times measured for other fluids.
The theory studied by the three researchers and their collaborators questions this belief. Unlike other approaches, the new theory does not assume that special exotic states, radically different from those in equilibrium systems, are needed in order to characterise glasses. The core guiding principle of the theory is that the same complete set of many body atomic states (quantum mechanical “eigenstates” or classical “microstates”) is sufficient to describe both (1) the supercooled liquids and (2) the equilibrium systems. A logical corollary of this principle enabled the prediction of all observable properties of glasses in terms of those of equilibrium systems. Consequently, the equilibrium melting temperature is of paramount importance.
In particular, according to this new theory, the viscosity of all glassformers should collapse onto a universal curve with the only important temperature scale indeed being that of equilibrium melting. As demonstrated by the team, the viscosity and relaxation data of 66 different liquids precisely collapse onto such a single scaling curve, thus suggesting a universal dynamic behaviour of supercooled liquids. Regardless of the theory that led to it, the collapse found by the team points to a previously overlooked link between equilibrium physics and glassy dynamics. Earlier studies of the team and their collaborators unveiled how solid-like rigid structures appear and grow as the temperature of the supercooled liquid drops.
Providing a clear understanding of the true nature of glassy systems will revolutionise the way we look at and use glasses 28
The work of the researchers intends to provide distinct answers and a valid theoretical framework to one of the most puzzling topics in condensed matter physics. Providing a clear understanding of the true nature of glassy systems will revolutionise the way we look at and use glasses and might offer a plethora of underlying industrial applications.
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Detail On which sectors of industry or research will this new knowledge of glassy dynamics have a profound impact? Glassy dynamics are ubiquitous. Due to their importance and universal prevalence, glasses are studied by physicists, chemists, materials scientists, and geologists. Industries rely on glasses for numerous applications. Concepts from glass and “spin-glass” physics have also led to potent algorithms for combinatorial optimisation and other computer science problems. Apart from structural glasses, similar dynamics appear in various electronic and magnetic systems. In principle, all liquids in nature can become glassy on supercooling. Our ideas and found universal collapse of the relaxation time are general, simple, and may apply for all liquids and glasses studied in industry and academia. What are the current limitations in research that have not allowed for a better understanding of glassy dynamics? Numerical simulations are hampered by long convergence time (indeed a quintessential feature of glassy systems is their sluggish motion). Earlier theories studied dynamics in high dimensional “energy landscapes” and hydrodynamics with memory effects. The difficulty underlying such approaches is that glasses involve many atoms. Direct calculations are impossible so various models and approximations were advanced. We aim to bypass these problems by using nature’s own solutions. That is, the equilibrium characteristics of the very same many-atom systems are known empirically. This information is then used to predict characteristics of supercooled liquids and glasses as averages of their equilibrium values. How can we have the capacity to manufacture new structural materials based on the knowledge of glassy dynamics? The current research suggests a link between equilibrium and glassy dynamics in all glassformers. Beyond the research
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discussed here, machine learning techniques used by ourselves and many others may suggest which new materials could be most suitable for manufacturing purposes. Additionally, viscosity plays a critically important role in glass formation through the dynamics of the crystal nucleation and growth (see next question). The ability to predict the temperature dependence of the viscosity from sparse data (which is possible from our results) may enable better control of nucleation and growth during cooling. What are the basic principles of supercooling a liquid to form a glass? To form a glass, one needs to supercool a liquid rapidly enough that crystallisation is bypassed and ultimately, at sufficiently low temperatures, the viscosity exceeds a critical threshold; the system then becomes rigid on typical observations scales. This rigid amorphous state is called the “glass”. How fast one needs to cool in order to achieve a glass depends on the system. For some materials such as silicates (that form window glasses), a relatively modest cooling rate suffices while for other systems (such as metallic liquids) far more rapid cooling may be necessary. What more is needed so that you and your team can have solid evidence for introducing this theory about the true nature of glassy systems? Our theory enables the calculation of any property of the glass as an appropriately weighted average of the equilibrium property. If various data become available on a specific supercooled liquid system, then one will be able to test whether the same weighted average may account in unison for all measured properties of the liquid. Thus far, we have largely tested dynamical data.
RESEARCH OBJECTIVES Dr Nussinov, Dr Weingartner and Dr Kelton's collaborative work has focused on the structure of glasses. FUNDING US National Science Foundation (NSF DMR 1411229, NSF DMR 12-06707, NSF DMR 15-06553); NASA (NASANNX 10AU19G); Simons Collaboration ("Cracking the Glass Problem") https:// scglass.uchicago.edu/ COLLABORATORS Dr Flavio Nogueira; Dr Christopher Pubelo BIO
Zohar Nussinov received his BSc from Tel-Aviv University and his PhD from UCLA. He has held postdoctoral positions at the Lorentz Institute and at Los Alamos National Laboratory. Since 2005, he has been a member of the physics department at Washington University, St Louis (where he is currently an Associate Professor). Kenneth F Kelton received his PhD from Harvard University in 1983. He is Professor of Physics and the Arthur Holly Compton Professor in Arts & Sciences at Washington University in St Louis, and is a Fellow of the American Physical Society. Nicholas Weingartner received his BSc from Saint Louis University in 2012, and his PhD from Washington University in 2017. He currently holds a position as a Modeling Analyst in the Underwriting, Research, and Control department of the GEICO home office. CONTACT Dr Zohar Nussinov Associate Professor Of Physics 353 Compton Hall Washington University, St Louis MO 63130, USA E: zohar@wuphys.wustl.edu T: +1 (314) 935 6272 W: http://www.physics.wustl.edu/people/ nussinov_zohar
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Dr Diyar Talbayev has been investigating the fundamental physics behind magnetism and how the interactions between the electrons in a material determine its magnetic and electronic properties 30
Complex Materials
Electronic behaviour in magnetic matter: insights from femtosecond and terahertz spectroscopy Magnetism in materials arises from the strange and exotic properties of the electrons within the material. There are a huge class of materials, including many rare earth elements, that are of particular use in a variety of computing applications, such as information storage and processing. By using novel experimental technologies to generate very short pulses of light in the terahertz region, Dr Diyar Talbayev, and his group at Tulane University, have gained an unparalleled insight into the magnetic dynamics of solid materials and the fundamental physics underlying these processes.
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hen thinking about magnetic materials, iron is probably the first to spring to mind. Iron was the first material found to exhibit permanent magnetism, which is why permanent magnetism is also known as ferromagnetism, after the Latin word for iron – ‘ferrum’. However, there are many more kinds of magnetism than just ferromagnetism, as well as a huge variety of compounds that show these exotic types of magnetic behaviours. Many of these are compounds that contain either heavy metals or rare earth metals that, at a microscopic level, form crystalline lattices with regular, periodic structures. Dr Diyar Talbayev at Tulane University has been investigating some of the fundamental physics behind magnetism and, in particular, how the interactions between the electrons in a material determine its magnetic and electronic properties. UP OR DOWN? There are many kinds of magnetism that are dependent on the properties of the electrons present in the material. Electrons have a property known as ‘spin’, which is really a quantum mechanical effect, but can
be thought of very crudely as the orientation of the electron as it rotates, where it can be either ‘up’ or ‘down.’ Although spin is an incredibly complex phenomenon, it is a very important property in determining the interaction of the electron with external electric or magnetic fields, or with other electrons. In most neutral molecules, electrons are typically found in pairs, with opposite spins. As there are an equal number of electrons with up and down spins, the overall net spin is zero. However, in ferromagnetic materials, like common iron bar magnets, there are some unpaired electrons. If all the atoms in an area, known as a magnetic domain, have their spins aligned, there is an overall spin in the material that results in ferromagnetism. SPIN DYNAMICS However, it is possible to change the orientation of spin of individual electrons, or lose the overall alignment of magnetic domains. If you hit an iron magnet hard enough, it can lose its magnetism because the magnetic domains become scrambled and there will be no overall spin alignment. Brute force is not the only thing that can interfere with the behaviour of magnetic materials. In the presence of an external
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Complex Materials
Ferromagnetic
Ferroelectric
Magnetically Polarised
Electrically Polarised
Magnetoelectric
electric field, the orientation of the spins can change in magneto-electric materials. Dr Talbayev’s group are particularly interested in an unusual type of magnetic behaviour known as antiferromagnetism. Here, the neighbouring ions have opposite spin alignments to each other. Antiferromagnetic and magneto-electric materials show very different properties to ferromagnets, but the ability to manipulate these using external electric fields means they show promise for potential applications in computer memory for the read/write processes involved in data management. However, probing spin states of electrons and determining their magnetic interactions has proved somewhat challenging. Nonetheless, Dr Diyar Talbayev is making use of terahertz light to do exactly that.
THE THZ REGIME Terahertz radiation is an electromagnetic wave which has a longer wavelength than microwaves but shorter than infrared light. Historically, it has been very difficult to generate light in this region of the electromagnetic spectrum. However, it is ideally suited to observing information on the spin states and dynamics of the electrons in materials and offers very high resolution information. This is because the energy of the radiation is comparable to the energy difference between the spin states of electrons in the material, so it can be used to selectively look at their quantum mechanical behaviour. THE ELECTRON MOVIE Dr Talbayev has been combining the utility of terahertz radiation with femtosecond laser
By using broadly applicable techniques such as time resolved terahertz spectroscopy, Dr Talbayev and his group have been able to look at a very diverse range of magnetic materials 32
pulses to perform time resolved terahertz spectroscopy (TRTS). Femtoseconds are incredibly short units of time that correspond to many of the timescales involved in the physics and chemistry of materials. These pulses are sufficiently quick to capture snapshots of motion of the electrons in the material. The pulse durations produced by a femtosecond laser are so short in time that the instantaneous power delivered by the laser is huge and easily able to perturb the electronic equilibrium of the material of interest – thus exciting the electrons and causing them to move. As well as being responsible for the magnetic properties of a material, the movement of electrons is what allows the flow of charge, which is why certain materials are conductive. For example, in metals, electrons can typically move freely around the material, rather than being localised to a single atom, meaning they can conduct electricity. Dr Talbayev has been using this to study the properties of the electron flow in magnetic metals. By probing the motion of electrons at different times after their excitation by a femtosecond laser pulse, information can be obtained on how the conduction process
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Detail What types of materials tend to show antiferromagnetic properties? Most crystalline materials that contain transition metal ions tend to show antifferomagnetic properties. Antifferromagnetism is more ubiquitous in nature than ferromagnetism. Ferromagnetism is a more obvious property, as a ferromagnet sticks to a refrigerator, while an antiferromagnet does not. Both these kinds of magnetism represent an ordered magnetic state. What will be the biggest breakthroughs arising from a more complete understanding of magnetic dynamics? Some of the biggest breakthroughs will be in the area of manipulation of ferromagnetic and antiferromagnetic domains by femtosecond light pulses. A femtosecond light pulse will be used to write and erase information in magnetic memories. This can potentially speed up the writing of information in computer memories by thousands of times. Another exciting area for groundbreaking discoveries is the manipulation of antiferromagnetic domains using the magnetic field of terahertz pulses. Terahertz pulses are not sufficiently strong for this yet, as outlined below in the final question. What types of applications will there be for antiferromagnetic materials? Antiferromagnets are used and will continue to be used in magnetic computer memories and data storage.
What are the current experimental limitations in trying to understand magnetic behaviours in materials? One experimental limitation is the weakness of the magnetic field of terahertz radiation. If made sufficiently strong, this magnetic field can potentially be used to control the electronic spin orientations via the interaction known as Zeeman interaction. However, more experimental development is needed to achieve a sufficiently strong magnetic field in a terahertz wave. A thousand-fold increase in this magnetic field is needed. What are your future plans for this research? My future plan is to investigate materials that are antiferromagnetic and also ferroelectric at the same time, or composite materials that are made of antiferromagnetic and ferroelectric constituents. Ferroelectricity is also a very useful property for data storage and processing. Ferroelectric domains are switched by an electric field. The marriage of magnetism and ferroelectricity promises fundamentally new kinds of devices, such as a memory bit with more than the usual two ‘up’ and ‘down’ states. My ultimate dream is to use the electric and/or magnetic field of a terahertz pulse to manipulate (read and write) magnetic and ferroelectric memory bits.
The marriage of magnetism and ferroelectricity promises fundamentally new kinds of devices works. As such, Dr Talbayev has been particularly interested in how these excited electrons are scattered on their journeys through the metal by ions of the crystalline lattice and by spin fluctuations.
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RESEARCH OBJECTIVES Dr Talbayev’s current research focuses on the optical and electronic properties of complex materials. He and his research team use time-resolved optical and terahertz spectroscopy to determine the magnetism and conduction of electrons in complex materials. FUNDING National Science Foundation (NSF) COLLABORATORS • Professor Keshav Dani (Okinawa Institute of Science and Technology Graduate University) • Professor Jiangfeng Zhou (The University of South Florida) BIO Diyar Talbayev was born in Almaty, Kazakhstan. He received a BS degree in Applied Mathematics and Physics from Moscow Institute of Physics and Technology in 1998, and a PhD from Stony Brook University in 2004. Since 2011, he has been an Assistant Professor at Tulane University. CONTACT Dr Diyar Talbayev, Principal Investigator Tulane University 6823 St. Charles Avenue New Orleans Louisiana USA T: +1 504 862 3183 E: dtalbaye@tulane.edu W: https://sites.google.com/site/ femtothz/
By using broadly applicable techniques such as TRTS, Dr Talbayev and his group have been able to look at a very diverse range of magnetic materials and really understand the role of the humble electron in shaping the materials’ magnetic and electronic properties.
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How new technology is stopping fire in its tracks After spotting an existing weakness in fire prevention methods, Geir Jensen, Technical Director at COWI Fire International, has spent the last twenty years researching and developing new ways to stop the spread of fire.
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Materials
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nventor and professional engineer Geir Jensen has a passion for devising practical solutions to problems. Through collaborations with scientists and the exploitation of opportunities as and when they arise, Jensen has recently brought to fruition an idea first envisioned 20 years ago. From idea to reality, the story of Jensen’s invention is an inspiring example of how far you can get with limited resources, as long as you have sufficient vision and ambition. CONFLICTING INTERESTS The challenge of designing buildings to withstand fire is an ongoing issue for the construction industry. In many cases, buildings, in particular their exterior construction, also need to be ventilated to prevent rot and fungus. However, in practical construction, ventilation and fire resistance are contradictory requirements: to ventilate a building you need gaps through which air can freely pass, but these gaps present a major area of weakness in the fire resistance of a building. This conundrum has for a long time been a major challenge to both research scientists and the construction industry. The question of how to make ventilation gaps fire resistant
Geir Jensen's research and inventions are paving the way for a new mode of thinking about fire resistance
has, until recently, been deemed too difficult and so generally ignored. Instead, research has focused on the parts of buildings that lend themselves more favourably to fireresistance measures. As a result, a lot of time and money has been invested in installing fire-resistance techologies in buildings which remain vulnerable to fire (due to the presence of unprotected openings like vents and gaps). In addition, there is a lack of standardised testing in this area, making it difficult for those requiring fire-resistance measures to make informed decisions. FILLING THE GAP There currently exists a range of methods for making ventilation gaps fire resistant. Intumescent materials that expand on exposure to flames and hot smoke gases create a seal against the spread of fire. However, these take a few minutes to fully seal, so still allow fire to spread in the critical early stages. An alternative technology, flame arresters, uses the principle of a quenching distance to prevent combustion. However, they have a very short working duration of a few milliseconds up to a few seconds. Evidently, even a combination of these two technologies would leave a significant time gap during which fire could spread through a building. Fascinated by this challenge, Jensen has spent the last 20 years designing and refining an invention which is set to revolutionise the world of fire resistance. FROM IDEA TO REALITY The story of Jensen’s invention begins in 1994, when he observed the construction of the Eidsvoll 1814, the constitutional building of Norway. The building contained many vertical ventilation shafts and Jensen was struck by the potential fire threat posed by these shafts and the lack of methods to prevent fires
Left: Over 20 years, cavity fire barriers for exterior construction evolved from the early types that performed only after being sealed by fire (flame and embers could penetate for the first few minutes). Middle: Perforated or labyrinth-type flame arrestors would block fire for the first five minutes, not after, and ventilated less efficiently. Right: The result is well ventilating malleable barriers for gaps or cracks of any size or form. These stand up to embers and direct flame as well as sustained fire, instantly at zero hours and for hours. (Coloured drawings by B Ă˜stman et al)
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Materials
spreading. This single observation prompted Jensen’s interest and research in this area and sparked a thought which has since proven to be revolutionary in this field. Motivated by a request for research from authorities and academia, in 1998 Jensen conducted a review of available mechanisms to prevent fire spreading through vents. This review gave him the idea of combining current technologies with new thinking to develop a unique and more effective method. Jensen's new technology, Firebreather, combines flame arresters and intumescent materials with a third component that acts as a heat sink. The heat sink material efficiently lowers the smoke gas temperature to below the ignition temperature of fuels, stemming the initial transfer of flames until the intumescent material becomes effective. This way, fire cannot penetrate at any time from the exact moment the fire exposure starts (zero hours) up to several hours later. This is key – all products are assessed on a time scale but it begins five minutes after ignition; that seemingly small window of the first five minutes is a crucial period when flames and embers could still be passing through other products. Over the next few years, Norwegian government funding allowed for prototype development. Prototype testing in 2002 proved highly successful, providing both immense satisfaction and the motivation to progress the design. Between 2002 and 2004 Jensen worked on refining his design and manufacturing an eave vent. 2004 marked a significant milestone in progress, as the invention was published as a poster paper at the annual Interflam conference. Although faced at times with a lack of interest and resistance from industry competitors, Jensen persevered with his vision. In the subsequent years, he filed patent applications, created building guides and handbooks, and addressed the lack of test standards. In a review of vented fire barriers in 2013, Jensen brought to light the lack of appropriate, comprehensive tests. In his review, Jensen states that most current tests do not adequately simulate likely fire scenarios, such as sudden flame. The conclusion to his report suggests re-developing an existing full-scale test to include exposure from zero hours by direct flame impingement. Based on the success of his previous design, Jensen is currently developing a linear
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Flame contact ignites combustibles in just one to three seconds. New test methods had to be designed in the USA and Europe in order to test whether vents instantly block flame attacks while they are still fully open
In terms of fire, a few seconds can make all the difference and, ultimately, by providing instant and lasting protection, Jensen’s inventions buy the time to reduce damage and loss malleable vent to seal irregular gaps and cracks. The vent can easily be installed by hand and is a fully reversible design, allowing it to be installed and removed without leaving a trace. This feature makes it particularly appealing for use in heritage buildings. With a patent application in progress, Jensen’s inventions are continuing to change long standing views on fire protection methods. PREVENTION IS KEY Clearly, Geir Jensen's research and inventions
Height of fire spread
are paving the way for a new mode of thinking about fire resistance. His vision, ambition and perseverance have resulted in unique new methods to stop fire from spreading through vents. These effective, affordable and easy-to-install technologies protect not only the structure itself, but also prevent the fire spreading to neighbouring buildings. In terms of fire, a few seconds can make all the difference and, ultimately, by providing instant and lasting protection, Jensen’s inventions are buying the time to reduce damage and loss.
Vented cavity barrier of perforated metal type fire spread delayed
No cavity barrier - or barrier fails to prevent entry of embers or flame before it is sealed
5m
Vented cavity barrier of wooden labyrinth type - fire spread delayed
Vented cavity barriers rated for fire resistance, embers and flame impingement during open and closed states 40 min
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New standards verify whether ventilating cavity barriers in gaps or cracks resist flame and fire consistently through the open and sealed states, i.e., from zero hours for as long as the fire partition time rating –green curve. This means they respond to fire as if they are airtight masonry or gypsum walls
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Detail Your patented technology combines the commonly used principles of intumescence and quenching diameter with a heat sink material. How does the heat sink work to prevent the spread of fire? The function of the heat sink is to delay heating of the unexposed side while the vent is still in the open state. Temperature must be kept below the ignition threshold of the gas emitted by the fire source. What fire scenarios should prevention methods be tested for? Until this invention, no ventilation fire dampers or air transfer grilles or other vented construction parts had been tested for fire resistance during the first five minutes after fire ignition. That was because, conventionally, fire resistance elements of buildings are inherently homogenous and airtight, so if an object resisted fire at five minutes it could be assumed it would have done so for the previous five minutes as well, so no need to test that initial period. In addition, the fire test furnaces require some minutes to run correctly and have been used as an excuse to not register failures at zero to five minutes. Fire dampers have always been tested as open from the start and they could not prevent fire spread during the first minutes before they closed. All fire dampers would therefore fail if tested from ‘zero hours’. So, the industry has continued to test dampers as if they were solid objects, i.e., failures are registered from five minutes onwards only. This delay in the testing is also partly due to the idea that fires take some time to build up in rooms so usually do not penetrate that early. This is valid for most indoor fires, though there are exemptions. For exterior fires, however, wind-driven embers and flames abound and penetrate vents in seconds without warning. All parties are agreed that conventional vents were not acceptable. Before my invention, attempts were made to close off vents manually if a fire was getting near, or use vents of metal
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sheet labyrinths to block flame, mesh to block embers etc. This new technology simplified all this. What effect has your research had on testing and standards in this field? My research and the ensuing technology has proven that “open state fire resistance” is technically feasible. Therefore, it was decided in North America to dedicate a new test method for direct flame impingement of open state elements (vented construction) during the zero- to five-minute period. This became the ASTM E2912 Standard. The test method for vents exposed to wildfire adopted that method, ASTM E2886. In Europe CEN decided to add a similar method to both new prEN 1364-5 and prEN 1364-6 Standards. In France a guide has been issued that explains how to apply open state fire resistance vents in facades (my technology) and refers to ASTM 2912 (Bois construction et propagation du feu par les façades En application de l’Instruction Technique 249 01/02/2017). You have been working on hypoxic (low oxygen) air technology for fire prevention. What are the limitations of this method? A constant low-oxygen indoor climate that is fire preventative but occupiable is a very simple and clean method. Except, the more that the low oxygen air leaks out and must be replaced, the more energy is required to refill. So, leaky rooms are ruled out. Low oxygen for occupation does not work for combustibles with very low ignition thresholds, as then the oxygen content in the room becomes so low it is uninhabitable.
RESEARCH OBJECTIVES Geir Jensen’s research focuses on preventing the spread of fires through the design and manufacture of specialised air vents for use in the construction industry. FUNDING Innovation Norway COLLABORATORS •T urid Buvik, Innovation Norway •A mal Tamim, COWI Gulf (now at Arencon, Canada) • Phil Grimwood, Cambridge Fire Research (now Technical Director of Dixon International Group) BIO Geir Jensen is a Technical Director of Fire Protection at multi-disciplinary consulting group COWI. He is also an inventor and is particularly interested in designing fire resistant solutions for the construction industry. CONTACT Geir Jensen Technical Director Fire Engineering Cowi AS Trondheim Norway T: +47 02694 +47 907 83 007 E: gjen@cowi.com W: www.cowi.com
What are your aspirations for 2017 and beyond? To see national codes require open state fire resistant ventilation where applicable, world-wide. Also, to see progress of my ideas on water mist and sprinklers for fire protection.
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Sparks fly in nanoscale engineering
Physics Engineering
Dr Carole Rossi and her collaborators at the Laboratory for Analysis and Architecture of Systems in Toulouse, France, as well as contributors from around the globe, are engineering nanoscale reactive materials. Coupling techniques used in the manufacture of microchips to the reactive chemical properties of metal oxides, the team are able to create atomic layers of reactants which have the potential to revolutionise our understanding of energetic materials.
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ince studying for her PhD, Dr Rossi has been interested in the ‘sleeping’ power of chemical energy and its potential for fast delivery of energy. Since the invention of gunpowder, scientists have understood the power of mixing potent reactants in close proximity ready for ignition and this arguably entered the nanoscale when chemists began synthesising molecular explosives such as nitroglycerine and trinitrotoluene (TNT). Bringing the required atoms into close molecular contact allowed for a massive increase in reaction speed and subsequent energy release. Dr Rossi recognised that, with modern manufacturing techniques, turning this devastating energy to small-scale practical purposes was a realistic possibility. Despite significant advances in the field of energetic materials (EM) manufacture, traditional EMs struggle to fulfil their potential at the micro scale. Due to intrinsic energy losses and the relatively slow reaction rate, they experience quench (the process stalls for lack of sufficient energy transfer) in even relatively large volumes such as steel and glass tubes of millimetrescale diameters. For these applications, more energetic materials are required which can overcome the high energy demand of micro- and nanoscale systems. Dr Rossi
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noted that some successes have been recorded by integrating metal particles, particularly aluminium (Al), to the propellant mixtures to increase the reaction rate. THE CHALLENGES OF SCALE Aluminium is particularly suitable for this role due to its rapid oxidation. Small particles, commercially available at low cost, are intrinsically stable due to their oxide coating. They increase the reaction rate through thermal transfer, a function of their high thermal conductivity. Dr Rossi evaluated that peak efficiency is reached when Al makes up 20% of the total propellant. This ‘doping’ of propellants improves conditions at the mesoscale (mm–cm), but is not sufficient to overcome thermal losses at the microscale. Despite several approaches investigating the use of alternative doping agents such as carbon nanotubes, or synthesis of nano-
propellants, or a combination of the two where the propellant is encapsulated within carbon nanotubes, Dr Rossi and others believe that an alternative solution exists. AN OLD TECHNOLOGY REPURPOSED Thermite reactions have long been known for their powerful thermal properties, being put to such heavy-duty uses as welding railway tracks together. In these reductionoxidation reactions a metal fuel, usually Al, is mixed with a metal oxide and brought to reaction temperature. The Al, which makes stronger and more stable oxygen bonds than its companion metal oxide, essentially steals this oxygen to do so, releasing a large amount of heat in the process. Dr Rossi and others have noted that this reaction, in contrast to those of traditional propellants and explosives, increases in speed and energy density as the materials are scaled down towards the nanoscale. Speed in particular can increase by a factor of ten when particle size is reduced from 20,000nm to 50nm, with ignition time decreasing by more than two orders of magnitude (from seconds to tens of milliseconds). LAYERING THE FOUNDATIONS Manufacture of suitable mixtures of these materials has proved complex, however. Sonic mixing of nano-powders in solution and the creation of gels by a similar method
Thermite reactions, in contrast to those of traditional propellants and explosives, increase in speed and energy density as the materials are scaled down towards the nanoscale
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Physics Engineering
Photo of one diced nanothermite-based ignitor chip being mounted and bonded to a pyrotechnical connector for integration in future energetic safety systems
Above: Photograph of two nanothermite-based ignitor chips: white squares are Al/CuO nanoscale reactive film made of hundreds of alternating Al and CuO nanolayers; yellow rectangles are the gold electrical pads used to supply the electrical energy for the nanothermite ignition. Total dimensions: 3.8 ×1.8 mm² Right: Photo of a flame generated by the reaction of Al/CuO nanoparticles mixed with PTFE nanoflakes
are limited by their ability to provide a sufficiently uniform mixture without impurities. More promising techniques have focussed on the deposition of alternate layers of the constituent elements, utilising methods common in the manufacture of electronic components. These overcome the limitations of mixing by exploiting precise control of the layer thickness (concomitant with particle size) and the elimination of impurities (often being performed under vacuum or in inert gas atmospheres). Nanostructuring of silicon, production capacity for which already exists in the semi-conductor market, has also proved effective in bringing oxides into close contact with potential fuel metal. PROBING DEEPER Although the functional properties of these new EMs has been well investigated, the detailed understanding of their underlying principles, and therefore the ability to generate theoretical models of novel materials, has not. Dr Rossi and her collaborators are focusing on probing the interfacial layers, the region where reactive layered nanostructures meet, and the core of their function. Using model surfaces created by atomically precise deposition methods, the team are
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able to derive detailed information through advanced imaging of the atomic structure. This approach allows them to assess the contribution of the interface layer between Al and the metal oxide to the reaction kinetics, as well as to the intrinsic stability of the material. OUT IN THE REAL WORLD With the goal of developing an atomic level understanding of the interface formation process, they are utilising cutting edge technologies for the modelling, creation and investigation of this layering approach to EM manufacture. The team will thus be able to transform the optimisation of this process, further refining a field which has seen rapid progress in recent years as the scale of operation has shrunk down from the mesoto truly nanoscale manufacture of EMs.
This work is vital to support the expanding field of microelectromechanical systems, where actuators and precisely localised thermal power generation are incorporated into a range of modern micro-electronic devices. From the microinjection of pharmaceuticals, to weight-critical propulsion systems in the space industry, the requirement for digitally controlled and precisely engineered EMs is growing. This is not to mention the challenges of manufacture of increasingly small-scale devices, where precise soldering and welding of components is vital to their operation. It is clear the work that Dr Rossi and her colleagues are doing, to uncover the atomic principles underlying these advances, is laying the foundation for fundamental changes in our understanding of highly energetic materials.
The team are utilising cutting edge technologies for the modelling, creation and investigation of this layering approach to energetic materials manufacture www.researchfeatures.com
Detail What is it about atomic scale engineering that fascinates you? I’ve always had a strong interest in the nanoscale world. As a student, I was fascinated by both the difficulty of appreciating the smallness of nanoscale and the fact that this scale defies the common sense of understanding. Atomic scale engineering not only gives new ways to see the matter, but it explores a wide range of methods to interact with atoms or molecules, to provoke their self-assembly on atomically well-defined surfaces and structures. Once the mechanisms controlling the self-ordering phenomena are fully understood, the self-assembly and growth processes can be steered to create a wide range of surface nanostructures from metallic, semiconducting and molecular materials. This offers something magical: we can redefine a new world just by organising atoms differently. Why did you focus on micropyrotechnics? During my PhD, I developed a keen interest in micropyrotechnics – they seemed a huge and powerful source of chemical energy that can be delivered very quickly. I imagined many devices that could provide high energy actuation within a very tiny volume. What are the principal real-world applications for EMs? Pyrotechnics are single-use devices containing energetic materials with a wide range of applications – the most famous example is air bag inflators. For three decades, many pyrotechnic applications have appeared with the apparition of new energetic compounds: biological neutralisation, brazing of materials and pressure-mediated molecular delivery. Safety devices, such as tiny pyrotechnics actuators, can now close a door in case of fire, while wireless pyrotechnic devices can even protect against avalanches. With the growth of energetic materials in society, new challenges accompany the development of new energetic materials and pyrotechnical systems. Among them is the necessity to engineer a class of safe and green energetic materials that can be programmed for designed missions.
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How do you see the EM field developing? Until recently, most energetic nanomaterials research has focused on enhancing the surface area, maximising the intimacy between reactive components, increasing the reaction rate and decreasing the ignition delay, while at the same time improving safety. For a decade, new insights into the atomic scale description of interfacial regions and new capabilities in surface functionalisation have provided alternative ways to control the nanomaterial thermal decomposition and sensitivity. By manipulating the reactive matter and its interfaces at the nanoscale, we can now easily produce targeted effects that cannot be achieved dealing with bulk materials only. These new categories of multi-functional energetic mixtures are expected to lead to major breakthroughs in propellants, explosives, pyrotechnical devices and weapons and will also constitute a breakthrough technology for national security by proposing fully integrated smart passive devices that can remain in sleep-mode for tens of years & wake up within nanoseconds. The potential impact of future advanced energetic materials and pyrotechnical systems are eagerly anticipated. However, we are still struggling to translate the fundamental advances reported in scientific literature into tangible applications. What are the benefits and challenges of international collaborations? Since I began my career, I have benefitted greatly from interdisciplinary collaborations. Innovation at the nanoscale requires an integrated and synergistic approach based on theory, experiment and technological developments. To this end, I want to stress the effort I have put into integrating critical collaborations with theorists in my lab (A Estève) and with experts in the characterisation of nanoscale mechanisms (Y Chabal, UT Dallas). The collaboration with chemists is also crucial as many of our engineering processes use wet-chemical processes. Close collaboration is required to bring together the host of characterisation techniques, theoretical modelling and the deep chemical insight developed by colleagues over the past two decades.
RESEARCH OBJECTIVES Dr Rossi’s research focuses on designing nanoscale reactive components (vapour deposited nanolayer and oxide or metallic quantum dots), assembling them into scalable 3D structures and finding the best nanotexture and nanomorphologies for achieving high energetic and rapid reactions. FUNDING • ANR • CNRS-INSIS • University of Toulouse/IDEX COLLABORATORS • A Estève (LAAS) • Y Chabal (UTD, USA) • C Tenailleau, P Alphonse (CIRIMAT) • B Warot Fonrose (CEMES) BIO Dr Rossi completed her PhD at the University of Toulouse under the guidance of Dr Esteve and undertook her post-doc at the University of Berkeley. She has been a research scientist for CNRS since 1998 and is now Director of IMPYACT joint laboratory between LACROIX and LAAS and CoDirector of Joint international lab, ATLAB. CONTACT Dr Carole Rossi CNRS Director of Research LAAS-CNRS NEO team 7 Avenue du Colonel Roche BP 54200 31031 Toulouse cedex 4 France T: +33 (0)5 61 33 63 01 E: rossi@laas.fr W: http://www.laas.fr
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Thought Leadership
ACS: Taking chemistry to Hollywood Science is everywhere. From your sofa to your car, pretty much any product you can think of would not exist without the work of science, and chemistry in particular. This fact is often under-appreciated by the public, but for Dr Donna Nelson of the American Chemical Society, she has made it her mission to change this. Following her work as the science advisor to Breaking Bad, she now hopes to continue her Hollywood adventure in the hope of changing the public perception and appreciation of science. We at Research Features recently spoke to her about this and much more.
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reaking Bad is regarded by many as one of the best American TV drama series ever. The numerous awards it has picked up over the years are testament to this. For those who have not seen it, the show centres on a school chemistry teacher who turns to drug manufacture in order to fund his own cancer treatment. The science underpinning each episode, especially related to the process behind the production of crystal meth, is fundamental to the show’s success. And it is here that Dr Donna Nelson’s work as the show’s scientific advisor has proved pivotal.
Away from her Hollywood duties, Dr Nelson is also the Immediate Past President of the American Chemical Society. She recently sat down with us at Research Features to discuss her role further, outlining why changing the public perception and appreciation of
science is so important. Hello Donna! What does your role as Immediate Past President of the American Chemical Society (ACS) involve? There are three of us in presidential succession simultaneously, and part of our collective role is to represent the ACS to the public. It is a voluntary position, so the members very much want to hear from us, because we represent them. Within that, each president gets to choose their own projects, related to something they are particularly interested in, or knowledgeable about. For me, I am very interested in communicating science to the public, which is also one of the reasons why I became the science adviser to Breaking Bad. What impact do you think Breaking Bad has had on the public, with regards to chemistry? I think it has moved everybody’s knowledge
I do not think that people realise how much science, especially chemistry, impacts their lives www.researchfeatures.com
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Thought Leadership
of chemistry forward. I have given hundreds of talks about the show, and at the end there is a Q&A period. Each time there are people in the audience who know more about Breaking Bad than I do, because they became so enthralled with it. One of the things that really amazed me about it was the number of students who would tell me they had become much more interested in science because of it. Some even phoned me up wanting quotations for their own science blogs, which of course I am always happy to provide. It is amazing how many times young people have said that Breaking Bad is what inspired them to start these blogs in the first place, so I am absolutely positive that it has influenced a great number of young people. I think a lot of people may not have known about the Drug Enforcement Agency (DEA) beforehand either. For instance, the show had assistance from the DEA on what the equipment in illicit meth labs should look like. They also advised which steps to omit from being shown on TV – they did not want it to be a cookbook for making illicit drugs. Why is it important to you to improve the presentation of science to the public, and ensure its accuracy on TV? The main reason is to influence the public to appreciate science. I found that it was Hollywood, the television and the movies, that had a real impact on the public’s perception of science. People watch TV series every week from their own living rooms, so I decided it was Hollywood that we needed to reach out to – but at the time it seemed impossible. That was until I read an article written about the show’s creator, Vince Gilligan, in Chemical and Engineering News – the American Chemical Society’s weekly magazine. He was saying that neither he, nor any of his writers, had any formal
science background or education. They were having to research their science content through the web. It was really important to Vince to get the science right, and it was proving to be really difficult. I read that and decided to volunteer my expertise. Breaking Bad was good because it helped to get science out there, but we still have a long way to go. It definitely benefitted me though, because it gave me a peek into how Hollywood operates. What was your input to the show? I gave input when they contacted me saying they were putting something into the script involving science. They would send me pages out of the script, asking me to draw chemical structures that they would put on the blackboard, or help them with the pronunciation of certain words or dialogue. I made set visits and was able to actually meet the actors and answer their questions about how scientists talk to each other, how they talk to their students, and what type of person becomes a scientist. Can you tell us more about the ACS’s background and what the aims of the society are? The ACS has a four-part strategic plan. The first part relates to its publication unit, which provides the very best chemistry-related information and knowledge-based solutions. A good example of this is the Chemical Abstracts Service (CAS), which assigns CAS numbers to chemical substances. The service is a division of the ACS, and was developed to overcome the limitations of other chemical naming systems. This is important for everybody who manufactures almost anything, because of the CAS number that is used to identify each chemical. Even attorneys and business
Dr Donna Nelson with Bryan Cranston (left) and Aaron Paul, during a Breaking Bad set visit.
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people know that the CAS number is used to identify chemicals, but they may not know that the number actually comes from the ACS. The second part is about helping members advance their careers. I am particularly happy with the way that the ACS gives underrepresented groups opportunities that one might not be able to get in academia or in the industry where they work, enabling them to get training and learn about leadership. The third part relates to education. ACS have their own self-certified degree, which students only receive if they take certain courses and fulfil certain requirements. The fourth goal is to communicate chemistry’s value to the public and to policy makers, including members of Congress. This is very important to me, because when I speak to people I will often say that I do not think the public appreciates scientists or science enough. Most science organisations and the government have done a pretty good job now of increasing the education aspect of science – there is a lot of science built into TV shows and even in our schools, etc. – but I do not think there is necessarily an appreciation for science. The general public are certainly becoming more science literate, and the students that come into my class now are so much smarter than they were 20 years ago, but I do not think that people realise how much science, especially chemistry, impacts their lives. You cannot name anything that does not contain chemicals, except a vacuum. Every single thing – car parts, furniture, carpeting, clothing – contains chemicals and people do not really fully appreciate that. That is why we have that as one of the ACS’ goals – to make the public not just understand science, but genuinely appreciate it.
I am very interested in communicating science to the public, which is also one of the reasons why I became the science adviser to Breaking Bad www.researchfeatures.com
Above: ACS President Donna Nelson Right: The American Chemical Society Building, in Washington DC
What impact do you think the ACS has had on advancing the broader chemistry enterprise since it was first established 140 years ago, and are there any accomplishments you are particularly proud of? I think the ACS has had a huge impact on every single scientific development, but particularly in two broad categories – the Chemical Abstracts Service and SciFinder. SciFinder, also produced by CAS, is a comprehensive database of chemical literature and is a core research tool. A lot of chemists do not understand what has gone into that, but it has been an immense effort. What developmental goals have you chosen for the ACS while you serve as the society’s primary spokesperson and representative? When I ran, I told the membership that I would try to accomplish whatever goals they wanted. I also sent emails out to every single member asking them what concerns they had. There were two main ones. One was about jobs and the other was about the public perception of science – which is my area of interest. To combat these, at the next ACS National Meeting we are going to have a symposium on how chemistry and science are presented in Hollywood, on TV and in the movies. For the jobs issue, we created a task force of people to look into
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it. I am currently in the process of writing up the results. Under the National Historic Chemical Landmarks program, the ACS grants landmark status to seminal achievements in the history of the chemical sciences and provides a record of their contributions to chemistry and society in the US. For you, which landmark has had the greatest impact? I really enjoyed visiting the birthplace of the American Chemical Society in Pennsylvania. It all began in a house that once belonged to Joseph Priestley, who discovered oxygen in 1774. It is still there and it has been converted into a museum. Amazingly, his lab is still there as well. On the hundredth anniversary of the discovery of oxygen, a lot of chemists met at his house and it was through a discussion at that anniversary celebration that they decided they needed a chemical society for the US. So, that is where the ACS was actually born – at that meeting and at that house. From a more personal perspective, your research into organic chemistry and longterm commitment to chemical research has seen you win numerous awards over the years. What does winning these awards mean to you? It means a great deal. One of the awards
which I won early on was a Guggenheim Award, which is very prestigious. I am very proud of that and I think that these things help you in your career. I remember when I was nominated for ACS Fellow I kept telling myself it was okay if I did not win, because I did not want to be disappointed. But then when I was elected to ACS Fellow, it meant everything. I think awards generally are very important – they certainly help one’s career, as they give you credibility in your work.
Contact American Chemical Society 1155 Sixteenth Street, NW Washington, DC 20036 USA E: service@acs.org W: www.acs.org @AmerChemSociety /AmericanChemicalSociety
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A coherent look at synchronised reactions
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Chemistry
Taking his inspiration from the way living cells appear to arrange reactions, Professor Tofik Murtuza Nagiev from the National Academy of Sciences of Azerbaijan is shedding new light on coherently synchronised reactions. Using carefully constructed algorithms based on observations of enzymes, Prof Nagiev has developed new models of how reactions may be synchronised on the macroscopic scale.
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rofessor Nagiev has spent many years researching the complex kinetics of chemical reactions – from his undergraduate days in Chemistry at the Azerbaijan State University, and throughout a long career in the Academy of Sciences. This extensive background places him in the perfect position to consider the next stage in the field, grouping these reactions together to form ensembles which progress quickly and with high selectivity for the final product. Synchronous parallel reactions, where reactions run at the same time but have no effect on each other, are not uncommon in chemistry and are therefore not of significant interest in the scope of Prof Nagiev’s work. More important are conjugated and interference reactions whereby the synchronised reactions affect each other, setting up oscillating conditions which vary product yields. ILLUSION IN MACROSCOPIC ORGANISATION Prof Nagiev notes that these effects can also be observed due to physical limitations of a system. Variations in the rate of diffusion of precursors to the active site of the reaction, for example in the Belousov-Zhabotinsky reaction (a classical example of nonequilibrium thermodynamics), give the false appearance of synchronisation. Prof Nagiev identifies this as a distinction between synchronous chemical reactions in the kinetic zone, which are coherent, and in the diffusion zone, which are not. However, both types of complex reaction are linked by the presence of intermediate compounds which are fundamental to the reaction process. There are both highly reactive intermediates, which are short lived and not included in the final product
equations and stable mediators which will appear in stoichiometric calculations (balancing reactants and products according to the laws of conservation of mass). INTERFERING INTERMEDIATES The presence of these intermediates evokes the concept of chemical interference, whereby complex chemical reactions are referenced in regard to their phenomena, as opposed to their component characteristics. This paves the way for energetically favourable, highly selective and economical production processes, which harness the synchronous nature of these complex chemical reactions. Prof Nagiev likens these ensembles of self-organising, self-assembling chemical reactions to the biochemical reactions found in living cells. Here interdependent reactions are brought to close proximity by the activity of enzymes, allowing for reaction rates which would otherwise be impossible to achieve. Mimicking this activity in chemical reactions is the goal of Prof Nagiev’s work, such that chemical production processes can be designed to respond to minor changes in composition of the reaction mixture in the same way that biological systems respond rapidly to essentially tiny perturbations. AN EXEMPLARY REACTION The only chemical reaction currently being exploited which approaches this situation is the use of hydrogen peroxide (H2O2 ) decomposition to drive the oxidation of substrates in the presence of a biomimetic catalyst. This process is used in production processes such as: methane oxidation to methanol; ethylene oxidation to acetaldehyde and ethanol; propane oxidation to isopropanol; propylene epoxidation and hydroxylation; and ethanol oxidation to acetaldehyde. These have all been
Chemistry is on the brink of establishing self-organising and self-assembling chemical systems www.researchfeatures.com
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Chemistry
Mechanism of the coherently synchronised catalase and monooxygenase (RH+H2O2=ROH+H2O) reactions
Theoretical kinetic curves for interfering reactions (primary 1 and secondary 2) of extreme (a) and asymptotic (b) types; Δ is the phase shift
From left: Professor Ahmed H Zewail from California Institute of Technology (Nobel Prize 1999), Professor Tofik M Nagiev from Azerbaijan National Academy of Sciences, Professor Rudolph A Marcus from California Institute of Technology (Nobel Prize 1992) and Professor Maria-Elisabeth Michel-Beyerle from Technical University of Munich, Germany
extensively studied by Prof Nagiev and his team in an effort to elucidate the kinetic similarities which might shed light on further applications of synchronous reactions. Ethylene oxidation is a particular case in point. Prof Nagiev has shown that, of the two main products ethanol and acetaldehyde, a simple change in reaction vessel temperature is able to significantly skew the production to one product or the other. At low temperatures, the predominant reaction is that of decomposition of H2O2 to oxygen, but as temperature increases this yield falls and ethanol takes over as the main product. A further rise then sees this ethanol become an intermediate itself and production of acetaldehyde becomes the predominant reaction. This is an example of chemical interference at work, as the primary reaction drives the secondary, which in turn decelerates the primary. The synchronisation of propane hydroxylation with H2O2 decomposition is a further example of this chemical interference in action. In this case, reaction time is the important
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variable. In the initial stages, production of oxygen through decomposition of H2O2 proceeds rapidly to saturation point; it is only once this has produced sufficient oxygen, that hydroxylation can begin to occur. This reaction then proceeds to utilise the oxygen intermediary to oscillating equilibrium, with complete consumption of H2O2. The kinetic curves of the catalase (decomposition) and monoxygenase (hydroxylation) reactions clearly show synchronisation and coherence, producing another example of tightly controlled chemical interference. OPEN HORIZONS These are just two instances where relatively simple reactions are shown to be coherently synchronised by establishment of their kinetic parameters and interactions. Prof Nagiev believes that this is just the beginning of a rapidly expanding field of chemistry which will harness interfering processes. His work
continues to develop algorithms which can assist in investigating and modelling these simple examples. Combining this with an improved understanding of their biochemical counterparts, the enzyme complexes and ensembles which drive cellular activity, will open new opportunities for improving production methods. According to Prof Nagiev, “Chemistry is on the brink of establishing self-organising and self-assembling chemical systems, [developing algorithms for] a group of chemical reactions to combine in an ensemble to obtain a final product, in a single reaction medium, with high selectivity, in a short time". In pursuit of this goal, Prof Nagiev’s team at the National Academy of Sciences continues to probe the current extent of this field, while realising and optimising novel experimental approaches to corroborate their models.
Prof Nagiev focuses on conjugated and interference reactions whereby the synchronised reactions affect each other, setting up oscillating conditions which vary product yields www.researchfeatures.com
Detail What first attracted you to the study of chemistry? I was brought up in a family of well-known chemical engineers. My father Murtuza Nagiev was almost fanatically devoted to science, in particular to chemistry. Since my childhood, I have unwittingly participated in the scientific discussions my father held with his colleagues in our house. Growing up my interest in the topics of these discussions was aroused, which subsequently resulted in my professional choice. What advice do you have for chemistry students today? Chemistry is so intimately related to the processes occurring in animate and inanimate nature that without its achievements there would be practically no advance in science or in other fields of knowledge, in respect of both fundamental and applied aspects. I believe that every student who devotes himself to chemistry will be useful in this field. In individual cases chemistry can even lead to fanaticism. I advise the young not to be afraid of new, unconventional ideas, not to be afraid of being misunderstood or even ridiculed. The thing that seemed inconceivable yesterday might become customary tomorrow. This has been repeatedly proven in the history of science. How does hydrogen peroxide advance our understanding of synchronisation in chemical reactions? Hydrogen peroxide is a popular oxidant, so called "green oxidant". This substance is widely represented in living organisms, cellular biochemical processes and in general chemistry. The vast majority of biochemical reactions are coordinated – in other words they are coherently synchronised. The same is observed in other areas of chemistry, where these reactions are called conjugate when the result of one reaction causes and accelerates the result of the second reaction. From this perspective, based on the use of hydrogen peroxide in reactions as an oxidant it is possible to develop
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a model of coherently synchronised reactions, and thereby to study chemical features of these reactions, to develop and evolve the general theory of coherently synchronised reactions. This is the reason I have become interested in this subject and have developed the theory of coherently synchronised reactions from the theory of conjugate processes: conjugate reactions are a particular case of coherently synchronised reactions. What do you hope the impact of your work will be? I believe that my work will enable the mechanism of coordinated interaction of biochemical reactions to be revealed. This mechanism might become the basis for the creation of innovative processes in chemical engineering. This will result in a situation where the principles of "green chemistry" (in terms of selectivity) will be reflected in the creation of new applied chemical processes. What is needed to advance the implementation of coherently synchronised reactions? Creation of such a design of chemical reactors, which will allow the most effective controlling of the rate of coherently synchronised reactions. This creates the possibility of creating chemical systems, including applied systems, in the most selective way.
RESEARCH OBJECTIVES Professor Nagiev’s work focuses on the macrokinetic theory of coherentsynchronous reactions interaction. Through his work, he has researched areas including the kinetics and mechanism of coherently synchronised reactions, radical chain reactions in the presence of hydrogen peroxide, catalytic reactions of gas-phase oxidation by hydrogen peroxide, oxidative fixation of atmospheric nitrogen, and many more.
BIO Tofik Murtuza oglu Nagiev is an Azerbaijani scientist, particularly recognised for his work in the fields of chemical kinetics, catalysis and coherently synchronised oxidation by hydrogen peroxide. CONTACT Prof Tofik Nagiev (VicePresident) National Academy of Sciences of Azerbaijan 111 H.Javid av., az-1143 Baku Azerbaijan T: +99412 538 47 07 E: tnagiev@azeurotel.com E: info@science.az W: http://www.science.gov.az/
On the other hand, examination of biochemical processes in the framework of coherently synchronised reactions will allow mechanisms of their coordinated interactions to be revealed. This will undoubtedly deepen our knowledge of the processes occurring in living systems. As a result of oxygen oxidation, usually at the initial stages, hydrogen peroxide is often produced and its role in coordinated biochemical processes has so far been insufficiently studied. Here one can expect completely unexpected results, which will allow the development of new approaches to the development of innovative technologies.
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An introduction to precise macromolecules based on molecular nanoparticles
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Materials
Dr Cheng and his student Dr Matt Graham examine a self-assembled giant molecular film with specific optical properties
Molecular nanoparticles are tiny building blocks on the nanometre scale with rigid molecular scaffolds. Dr Stephen Cheng from the University of Akron is exploring their potential for modularly making precise macromolecules with unique properties in greater depth and in doing so he is uncovering the possibility of creating new materials.
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n the beginning of the 1960s, Richard Feynman raised the question: ‘What would the properties of materials be if we could really arrange the atoms the way we want them?’ Not only has this question led to the burgeoning of nanoscience, but it has also inspired many scientists to develop “precise” macromolecules (polymers), whose properties and functions are determined by the hierarchical structures assembled in an organised manner across multiple length scales from nano-building blocks. This is exactly the focus of Dr Stephen Cheng’s work in the Department of Polymer Science at The University of Akron. His primary research is dedicated to the
condensed states of polymers, liquid crystals and surfactants, including phase transitions, thermodynamics and kinetics of metastable states, ordered structures and morphologies, surfaces and interfaces in electronic, optical, and advanced functional hybrid materials. His recent focus is on the construction of giant molecules (precisely defined macromolecules) with molecular nanoparticle building blocks and the illustration of the underlying physics for technological applications. These are undoubtedly the key to 'bottom-up' nanofabrication technology, offering a distinct scientific understanding of selfassembly and a unique route to the creation of unconventional hierarchical structures and dynamics.
Molecular nanoparticles ... offer a distinct scientific understanding of selfassembly and a unique route to the creation of unconventional hierarchical structures and dynamics www.researchfeatures.com
THE HOLY GRAIL OF POLYMER SCIENCE There are several key aspects which form the core of Dr Cheng’s research. Selfassembly is the process whereby preexisting components spontaneously form ordered structures and patterns at any scale driven by molecular interactions and thermodynamics. Down to the nanoscale level, self-assembly relies on the structural parameters of each individual molecule. They include shape, charge, functional groups, configuration, and conformation – the elements required to allow molecules to associate with one another to produce sophisticated functional systems. Control of these elements in macromolecules isn’t trivial. In fact, it is the Holy Grail of polymer science to do it precisely. Macromolecules are divided into two classes: natural macromolecules, such as proteins and nucleic acids, and synthetic polymers, such as common plastics, nylon and Plexiglas. In fact, synthetic polymers typically consist of repeating molecules that are covalently linked (they share electron pairs between their atoms) to one another, and whose properties are determined by their overall molecular weights, polydispersity, chain topology, etc. By contrast, natural macromolecules usually possess precisely defined structures, including molecular weight, sequence, and stereochemistry, to achieve predetermined functions at a level not paralleled by synthetic polymers. In other words, the construction and assembly of macromolecules demand the control of the polymer’s primary chemical structure with molecular precision. Even though this ‘control’ has been the fundamental topic of research in polymer science for decades, there has been limited success. It hinders our understanding of macromolecules and the use of them to generate systems with supramolecular structures that can efficiently transfer and amplify their individual molecular properties and functions through to macroscopic levels.
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Materials
A NEW CLASS OF SELF-ASSEMBLING MATERIALS A giant molecule, much like its name suggests, is a covalently bonded structure that contains a great number of atoms. Typical examples of such molecules that have the capacity to form giant structures include silicon, silicon dioxide, diamond carbon and graphite. Dr Cheng has added a new branch to the family of giant molecules using selected, precisely functionalised, molecular nanoparticles. These elemental building blocks are called nano-atoms and it is their exact and specified properties (such as their volume, symmetry, and surface functionalities) that Dr Cheng is exploiting in order to construct new prototype giant molecules in a modular, efficient, and precise manner and to afford on-demand hierarchical structures via triggered assemblies. In fact, according to research papers published by his group in recent years, the self-assembly of giant molecules, such as giant polyhedra (e.g., giant tetrahedra), giant Janus particles, and giant surfactants, exhibits unconventional phases and structures typically not found in soft matter. Moreover, their formations and structures are highly sensitive to their primary chemical structures, a trait that is common for small molecules but not conventional macromolecules. Controlled heterogeneity is the key in the design, making giant molecules a new class of self-assembling materials in addition to surfactants, amphiphilic polymers, and dendrimers. THE MATERIALS GENOME APPROACH TO GIANT MOLECULES Dr Cheng’s group has already proposed a modular approach to construct precise macromolecules using functionalised molecular nanoparticles as the fundamental building blocks. One can compare this process to constructing a structure with LEGOTM: the overall properties of this structure are defined by each LEGOTM brick and, ultimately, these giant molecules can be regarded as size-amplified small-molecule
Dr Cheng and his student Dr Matt Graham conducting the small angle X-ray scattering experiments that they use in their lab for determining supralattice structures
analogues. By doing so, more specifically, the group aims to apply the Materials Genome approach to macromolecules. Multiple molecular nanoparticles could be incorporated into a giant molecule with precisely defined composition, sequence and geometry in a series of ‘click’ reactions. Owing to the fact that such ‘click’ reactions are very selective and efficient, the group can then manipulate primary structures of single molecules, even ones with high molecular weights. The subsequent selfassembly will be propelled by various interactions (hydrophilic and hydrophobic) between these nanoclusters and the overall molecular symmetry. Each building block will exhibit distinct heterogeneity, and hence influence the respective self-assembly
Dr Cheng’s group envisions the construction and introduction of precise nanostructures that are not only scientifically intriguing but are also technologically relevant 52
process. This is exactly what is needed in order to build structures whose properties will be fine-tuned according to the molecules (nano blocks) inserted. Eventually, the final materials would demonstrate the properties that are the phenotypes of the “genes” of corresponding building blocks, much like how the genome defines life in biological systems. The importance and significance of Dr Cheng’s work in the Department of Polymer Science at the University of Akron, OH, is self-evident as it intends to improve education and to explore the very frontiers in soft materials-based sciences, engineering and technologies. This scientifically innovative research aims to design and synthesise giant molecules with controlled heterogeneities and defined hierarchical structures via precisely arranged nano-building blocks. Ultimately, Dr Cheng’s group envisions the construction and introduction of precise nanostructures that are not only scientifically intriguing but are also technologically relevant, thus triggering a revolution in the field of polymer science toward materials defined by the genes of each component.
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Detail Why are functionalised molecular nanoparticles so important? Unlike traditional polymers that usually exist as random coils, molecular nanoparticles are precisely defined molecular moieties with rigid conformation. Their shape, functional groups, symmetry, and molecular weight are predetermined and can be modified with molecular precision. Moreover, the diversity of molecular nanoparticles is tremendous. They are found to possess a broad range of compositions, structures, and functions. Therefore, they can serve as unique and versatile building blocks for new macromolecules and materials. What more is needed in order to effectively succeed in the team’s objective to unravel and introduce functionalised molecular nanoparticles? First of all, we need to develop methods for the selective functionalisation of molecular nanoparticles. There are usually multiple functional groups on them. Controlling the location and efficiency of functionalisation is the first step in controlling their 3D arrangement and assembly. Second, we need creative ways to covalently bond molecular nanoparticles of distinct features. In other words, we need chemistry that can bridge materials in different categories for hybrid materials with high efficiency. Third, we need to master their interactions so as to manipulate their assembly across all length, time, and energy scales to the structures that we desire. Heterogeneity at larger length scales: approximately up to what length scales does your group target (molecular weights)? Heterogeneity at different length scales can be controlled by different means. At larger length scales, traditional “top-
down” approaches are very effective in creating heterogeneity within order. At smaller length scales, the “bottom-up” approach works with molecular precision. It is the mesoscale, from 1–100 nm, that poses the most significant challenge to materials scientists. This is exactly the length scales that we are working on and whose structures our materials are good at controlling. The group has already suggested a means to construct giant molecules – using MNPs. Is this the only approach to generate such supramolecular structures or is it the one you prefer? This is definitely not the only approach. I would say that this is one of the most effective ways to generate supramolecular structures at 1–100 nm scale. Giant molecules fill the gap between self-assembling small molecules and traditional amphiphilic block copolymers. Can you name a few specific industrial applications that can take advantage of the introduction of this innovative technology? IT technology perhaps would benefit the most from our technology in the creation of sub-10nm structures and patterns. Other potential industrial applications include functional membranes (e.g., for water treatment), optoelectronic displays and components, antibody engineering, and advanced diagnostics. I anticipate that the application would be unlimited since this class of materials’ functions are defined by the genes of the virtually limitless types of building blocks.
RESEARCH OBJECTIVES Dr Cheng’s research focuses on the condensed states in polymers, liquid crystals, surfactants, micelles and hybrid materials. Within this, he looks into the interactions, dynamics and structures of particular materials. FUNDING National Science Foundation (NSF) COLLABORATORS Prof Wen-Bin Zhang (Peking University), Prof Takuzo Aida (University of Tokyo), and Prof Sharon Glotzer (University of Michigan) BIO Dr Cheng received his PhD from Rensselaer Polytechnic Institute in 1985. He has been elected to the National Academy of Engineering in US. He currently holds the Frank C. Sullivan Distinguished Research Professor, Robert C. Musson and Trustees Professor at the University of Akron. He has also received numerous awards, including the Presidential Young Investigator Award, John H Dillon Medal and Polymer Physics Prize. CONTACT Dr Stephen Cheng Goodyear Polymer Center Room 936, The University of Akron Akron, Ohio 44325-3909 USA T: (330)972-6931 E: scheng@uakron.edu W: https://www.uakron.edu/dps/faculty/ profile.dot?id=6fa727f6-c3a0-4b5a-97640ee2e975da2b
Molecular nanoparticles can serve as unique and versatile building blocks for new macromolecules and materials www.researchfeatures.com
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"Forest" of optics on an air-float optical table enables efficient light conversion from a commercially available laser amplifier to ultrafast light pulses with tunable wavelengths, bandwidth, duration, and power. Shown here is a home-built compact two-stage noncollinear optical parametric amplifier that generates a 480 nm femtosecond pulse to initiate the photochemical reaction of interest. Now the molecular movie starts!
Chemistry
Creating ‘molecular movies’ with ultrafast Raman spectroscopy Dr Chong Fang is an Associate Professor of Chemistry at Oregon State University. He leads a team of researchers in developing ultrafast Raman spectroscopy methods to allow the capture of real-time molecular movies. The ability to follow a process (biological or chemical) step-by-step offers huge potential in both understanding and control. Ultrafast Raman spectroscopy is an emerging structural dynamics technique which offers just that, and is contributing to significant progress in developing both biomolecular sensors and novel functional materials. of biological processes and novel functional materials. In particular, this is within the area of photochemistry where reactions are pivotal in energy transfer processes on ultrafast time scales. Not only are the photochemical reactions of importance to Dr Fang and his co-workers, but he is also especially interested in the development of the FSRS technique through these studies.
RESEARCH IN FUNDAMENTALS DRIVES IMPACT IN APPLIED WORLD Femtosecond stimulated Raman spectroscopy (FSRS) technology can have significant implications within a number of fields. The work carried out by Dr Fang and his group is heavily driven by the need to do relevant engaging research which not only investigates the fundamentals, but can be applied across disciplines. A key interest is the structure–function relationships, which contribute to the understanding and tuning
ULTRAFAST PHOTOACID DYNAMICS The photoacid (molecules which become more acidic on exposure to light) pyranine was selected for study by Dr Fang and coworkers to undergo functional motions on femto- and pico-second (one millionth of a millionth) time scales following the actinic photoexcitation. These structural dynamics include excited state proton transfer (the hydrogen atom charge exchange between partners) and vibrational cooling (off-loading excess excitation energy into surroundings).
INVESTIGATING PHOTOCHEMICAL REACTIONS IN ACTION Dr Fang and co-workers have conducted several cutting-edge studies on photosensitive molecules that exhibit previously unknown structural dynamics on ultrafast time scales.
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Dr Fang and his group focus on ultrafast Raman spectroscopy, capturing molecular snapshots on the time scale of molecular vibrations
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aman spectroscopy exploits the inherent motions or vibrations of molecules and allows a structural snapshot to be gained; the output can be interpreted to display a molecular fingerprint. The work of Dr Fang and his group focuses on ultrafast Raman spectroscopy with femtosecond resolution (one billionth of a millionth of a second), accessing normally hidden molecular snapshots on the time scale of molecular vibrations. As such, if a molecule is undergoing some sort of transition, then it is possible to capture the pertaining atomic choreography along the transition and when combined, give a riveting molecular movie that may reveal mechanistic information.
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Chemistry
to reach the green fluorescent state. Structural rearrangements around key residues, affecting the hydrophobicity of the chromophore and hydrogen bonding networks, also inhibit ESPT reaction in the presence of calcium ions.
Tracking atomic motions (including the proton) of a chromophore (see centre) after the light-induced electronic excitation reveals photoacidity in action
Time-resolved FSRS paints a panoramic portrait of molecular events inside a GFP-based biosensor that changes emission colour upon binding calcium ions
Typically, such processes are followed using time-resolved Stokes (the sample scatters light at a lower energy than the incident laser) Raman spectroscopy to observe the excitedstate dynamics. Dr Fang and co-workers, however, looked at processes that trialled a combined Stokes and anti-Stokes (the sample scatters light at a higher energy than the incident laser) measurement approach. This offered the potential to access a greater depth of information about excitedstate relaxation mechanisms by detailed comparison between multiple Raman modes.
were first identified in jellyfish, and comprise a chromophore (a group responsible for colour) stimulated by light and embedded in a protein pocket. Combining FPs with biosensors (molecular devices containing a biological and physiochemical component) in a single device opens up the potential to exploit the fluorescent property in bioimaging for the study of particular biological processes, such as neuron firing (sending out brain messages) and metastasis (spread of malignant cancer cells). Unravelling the photoinduced structural dynamics of the FP-based Ca2+ biosensors can guide their rational design for better biosensing technology which, until recently, has been achieved via time-consuming trial-and-error methods.
The integral spectroscopic approach was made possible by using a Raman probe which covered a broader spectral range. This probe can be readily tuned to the dynamic region of interest, enhancing signals from the transient species. From this newly improved experimental set up, Dr Fang and co-workers uncovered the intrinsic conformational dynamics during the photochemical reaction and identified a two-phase (fast and slow) energy dissipation pathway. FLUORESCENT PROTEIN BIOSENSORS FOR CALCIUM IMAGING Using the ultrafast Raman technique, Dr Fang and co-workers have unravelled the excited state conformational dynamics of fluorescent protein (FP) Ca2+ biosensors. FPs
Dr Fang and co-workers studied several emergent GFP-calmodulin-chimeric calcium biosensors using time-resolved FSRS. As in the studies of the photoacid, tunable Raman pump and probe pulses were employed to enhance the signals from the shortlived excited state species. In both cases, the structure–function role of the protein calcium biosensor was revealed, including how the calcium ions allosterically modify the FP chromophore pocket environment and affect the excited state proton transfer (ESPT) via characteristic vibrational motions
The cross-discipline nature of Dr Fang’s work means that the insights revealed through his team’s research have enhanced scientific understanding, and determined the potential for technological developments 56
A PLATFORM TO ELUCIDATE AQUEOUS ALUMINIUM CHEMISTRY IN REAL TIME Work by Dr Fang and co-workers has also helped to address the gap in knowledge of aqueous aluminium (Al) chemistry – hugely important in the modern world and especially in industries such as electronics and soil chemistry. Dr Fang’s team and collaborators have developed a powerful platform capable of overcoming the challenges faced in the selective synthesis and in situ characterisation of flat Al13 clusters – environmentally “green” precursors (component building blocks) of electronic thin films such as sapphire. They employed ground-state FSRS and developed the technology using a Raman probe pulse that could measure a wider range of Raman signals including the low-frequency modes, generated by a unique optical approach of crossing two femtosecond laser pulses onto a thin transparent medium, exposing the spectral region to observe signals from the nascent Al nanoclusters. Using the modified FSRS technique to target the formation of the flat Al13 cluster as a function of acidic pH values (potential of hydrogen in solution), the group identified an efficient and successful synthesis route (via an electrochemical method). Combining computational results with spectral data from the experiment, the FSRS technique further allowed the multi-staged reaction species, including an Al7 intermediate and the final Al13 cluster, to be determined and their evolution over the reaction to be followed. This established a three-step pathway from the starting components to the Al13 target cluster in water, the omnipresent solvent. This collage of snapshots into the work of Dr Fang presents femtosecond stimulated Raman spectroscopy as a powerful technique for tracking photochemical reactions in solution – it has not only been shown to be versatile, but it can be applied to a diverse range of problems as well. The crossdiscipline nature of Dr Fang’s work means that the insights revealed through his team’s research have both enhanced scientific understanding, and also determined the potential for technological developments from the bottom up across a number of important fields with social benefits.
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Detail What was the catalyst to you advancing ultrafast Raman spectroscopy for molecular movies? Understanding the structure–function relationships and how chemical reactions occur in real time has been the “holy grail” for scientists and engineers. Trained as a physical chemist, I was fortunate to study under two renowned molecular spectroscopists, the late Prof Robin Hochstrasser at UPenn and Prof Richard Mathies at UC Berkeley. My PhD thesis focused on the structures and dynamics of alpha-helices and drug–enzyme complexes in water and membrane environment at thermal equilibrium, and it was an interesting transition for me to move across the country and investigate the photochemistry of green fluorescent protein! Once I discovered the power of ultrafast Raman and the intriguing spectral data like a Picasso painting, I was drawn to the intricate and compelling molecular “movies” that we capture from solution precursors of high-quality thin films to protein biosensors which can track calcium ion movement in living systems. Who do you hope will benefit from this ultrafast FSRS technology? The main beneficiaries of the FSRS technology are scientists, researchers, engineers, and developers in physical chemistry, chemical engineering, materials science, energy sectors, and biomedical fields. We envision that a fundamental mechanistic understanding of chemical reactivity and reaction pathways can truly provide targeted rational design principles to improve the functionality and usefulness of a wide range of molecular “machines”. We have started a number of exciting collaborations with chemists, materials scientists, protein engineers, and optics experts across the world to accelerate the discovery pace and research impact. Why is it important to you to study both scientific fundamentals as well as their applications in the wider world? One thing that excites me the most about working at a public university is that I can teach a large number of students, do research, outreach, have an impact on people surrounding me, and vice versa. It
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is important to remain relevant as a scientist in this modern age not just for the need to support a research lab, but also for your own inner passion and drive. Curiosity is second nature to human beings and the pursuit of new knowledge is satisfying in its own merit. However, a visible impact on the current applications of those functional molecular systems under FSRS investigations should elevate our research to a new height and keep every team member highly engaged. In your experiments, you follow a reaction as it happens, on ultrafast time scales. What challenges does this kind of experimental set-up pose? I consider myself lucky to be able to develop a powerful structural dynamics toolset at OSU Chemistry and shed light on many exciting yet underexplored reactions. Using the molecular movie analogy, we are not directing the atoms to move, instead we gently excite and push them in a coherent way then watch the ensuing actions and consequences. The main challenges arise from achieving the balance between force and location for the push, and the resolving power of our “camera” capturing those fine details of the excited molecules. One effective strategy has been the wavelength tunability of our sequence of laser pulses that can be individually and precisely controlled. Where do you plan to take this ultrafast FSRS technology next? Our journey into the intriguing world of photochemistry has just started. We have been fortunate to catch a glimpse of the multidimensional reaction coordinate of materials transformations and biosensor responses, but there is so much more to learn about these molecular systems. Building on the knowledge and expertise we have gained over the years, we are poised to further develop the FSRS technology to be more versatile and user-friendly with fieldproven operating procedures, tips and tricks, and higher resolving power with less sample concentration and reduced laser powers. Our future interests include the engineered protein biosensors with genetic code expansion, super-photoacids, and molecular motors that modulate their emission properties under light irradiation.
RESEARCH OBJECTIVES Dr Fang’s work focuses on the development and application of ultrafast Raman technology in tackling some of the outstanding and foundational questions in materials and biological sciences. His research elucidates hidden reaction pathways of a wide range of light sensitive molecular systems during photoinduced transformations, which have strong implications for metal speciation in solution, optoelectronics, light harvesting, bioluminescence, optogenetics, and much more. FUNDING National Science Foundation (CAREER grant) Medical Research Foundation of Oregon COLLABORATORS Dr Robert E Campbell (University of Alberta); Dr Douglas A Keszler (Oregon State University); Dr Dan Huppert (Tel Aviv University); Dr Ryan A Mehl (Oregon State University); Dr Weimin Liu (ShanghaiTech University); Ms Breland G Oscar, Yanli Wang, Mr Longteng Tang and Liangdong Zhu (Oregon State University) BIO Dr Fang graduated from University of Science and Technology of China (USTC) with a dual BS in Chemical Physics and Applied Computer Sciences. He received a PhD in Physical Chemistry at the University of Pennsylvania before starting a postdoctoral fellowship at the University of California, Berkeley. He is currently an Associate Professor of Chemistry at Oregon State University. CONTACT Dr Chong Fang Associate Professor Department of Chemistry Oregon State University Corvallis, OR 97331 USA T: +1 541 737 6704 E: Chong.Fang@oregonstate.edu W: http://oregonstate.edu/colleges/ chem/fang/
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Dr Morris thinks that an interesting family of compounds, known as metal organic frameworks, might be the key to overcoming the current instability and limitations of existing solar cell devices
Solar Energy
Metal Organic Frameworks – the future of solar energy? Clean, affordable energy is one of the most pressing issues in modern society. However, despite huge increases in the efficiencies of solar cell technologies in recent years, the widespread adoption of solar energy has been hampered by the often-uneconomical cost of solar materials and issues with energy storage. Dr Amanda Morris and her group at Virginia Tech have been overcoming these challenges by exploiting metal organic frameworks to build new generation solar cells and develop new methods, inspired by nature, to store the energy harvested from the sun.
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n one and a half hours, enough solar energy hits the earth to power human civilisation for a year. The huge amount of potential energy to be harnessed is part of the reason why solar energy is an attractive option as a renewable energy source. However, the challenge has been to develop new technologies capable of converting this vast amount of light energy into electricity. Solar cells are the most common devices for achieving this conversion. At present, most commercially available solar cells make use of silicon-based devices. These devices use two sandwiched layers of doped silicon, with one layer of n-type and another of p-type silicon. The p-type silicon is electron deficient, whereas the n-type has an excess of electrons. As such, both layers will try to lose or gain electrons until they are stable. However, at the interface between the two types of silicon, a junction is formed that acts as a barrier to the movement of any electrons between the two layers. Nonetheless, as soon as the silicon absorbs light, this gives the electrons enough energy to traverse the barrier and move around the circuit, making an electrical current flow.
and, as they can be incorporated into thin, flexible films, have led to the production of significantly more lightweight solar panels. This, and generous tax incentives for ‘clean energy generation’, have led to their increased adoption. However, silicon devices may not be the entire future of solar energy conversion. The silicon required for solar cells must be of a very high purity, and the refinement processes involved in making the thin
wafers that ultimately end up in devices are energy intensive and produce large amounts of chemical waste that poses serious environmental issues. Therefore, researchers, such as Dr Amanda Morris at Virginia Tech, are looking into alternative materials for next generation solar cells. Potential materials that have proved attractive candidates for both cost and efficiency reasons include dye-sensitised and polymer-based solar cells, as well as perovskites. However, Dr Morris thinks that an interesting family of compounds, known as metal organic frameworks (MOFs), might be the key to overcoming the current instability and limitations of existing solar cell devices. MOFS IN THIN FILMS MOFs are compounds composed of metal ions or clusters, with various other chemical motifs, to make 1D, 2D or 3D structures. For example, it is possible to create MOFs that act as ‘molecular cages’, with cavities inside capable of trapping small molecules for applications such as hydrogen storage. MOFs can be incorporated into thin film arrays as a type of ‘sensitiser’ for solar cells. Whereas in a traditional silicon solar cell, all the electrons involved in the current come from the silicon itself, in a sensitised solar cell, a material acts as a rich ‘electron source’. These electrons are then transferred to an electron acceptor, typically TiO2 – greatly increasing the overall current produced. Dr Morris’s research has shown that MOFs are potentially a very attractive candidate for sensitisers as they are very stable and can absorb large amounts of light energy. This
Currently, silicon-based cells are leading the market in terms of the conversion efficiencies
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Solar Energy
leads to a good efficiency in comparison to more traditional dye sensitisers. Dr Morris’s work does not focus solely on practical applications though – her group are also working to understand the fundamental relationship between the structure (both molecular and 3D) of such MOFs and observed photophysical properties. This will help with predicting what types of compounds are likely to make good candidates for use in energy applications, as well as enhancing our understanding of the fundamental physics of energy transport. ARTIFICIAL PHOTOSYNTHESIS AND SOLAR FUELS MOFs may have another powerful application in the world of solar energy. With the efficiency of solar cells improving year on year and decreasing manufacturing costs, solar energy generation is quickly becoming a viable alternative to fossil fuels. Now, the main limitation is finding ways to store the generated electricity, until it is required, to ensure a continuous electricity supply. Traditional battery technologies still fall far short of the capacities required.
Metal Organic Frameworks
Quantum Dot Sensitised Solar Cells
Artificial Photosynthesis
Hybrid Bulk Heterojunction Solar Cells
One option is to take some inspiration from nature, and in particular, the photosynthesis process in plants. Photosynthesis is how plants convert solar energy into chemical energy to fuel their growth and drive the chemical processes necessary for their survival. Dr Morris has been investigating how this process could be done in the lab, a type of ‘artificial leaf’, and how MOFs could be used to help make this more efficient. The biggest challenges in emulating the processes in plants is finding a way to efficiently split water into hydrogen and oxygen using light, in a process called photo-driven water splitting. The hydrogen can be stored as a ‘solar fuel’ and then combusted, in a similar fashion to current fossil fuels, when additional energy is required. The versatility of MOFs means they can be used to catalyse several steps in the complex process and can even be used to safely store the hydrogen gas produced. Dr Morris’s group has recently shown how MOFs can be used to improve the efficiencies of several steps of the water splitting process, but there is no doubt that this is just one of many areas in which Dr Morris will continue to spearhead further crucial developments in clean energy generation.
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Why MOFs? • Layer-by-layer design - integrated light harvesting, charge separation, and catalysis in one array • Aqueous stability (pH 2-11) • High surface area • The molecular nature and crystallographic orientation afford synthetic diversity and structural rigidity for systematic studies and control over reaction mechanisms
With the efficiency of solar cells improving year on year and decreasing manufacturing costs, solar energy generation is quickly becoming a viable alternative to fossil fuels www.researchfeatures.com
Detail What do you think are the biggest remaining obstacles to more widespread adoption of solar energy technologies? The major component of solar cell installation cost comes from the balance of systems. This refers to the inverters, racking, cables, fuses, etc. that are also required when installing a solar module. When it comes to controlling the cost of solar installations in the short term, we need to address these costs and facilitate advances in these technologies. Additionally, the intermittent nature of the sun necessitates storage technology. Whether that solution comes from a stepchange in battery capacities or methods to convert solar electricity into chemical fuels, the scientific community must solve this challenge for widespread solar energy utilisation. Do you think the future of solar cells will involve a mixture of technologies existing simultaneously or is there the possibility of one type ‘winning out’ over the others? History, existing manufacturing capacity, and infrastructure are predictive of dominant technology. Take the energy sector: fossil fuels dominate (85%) even though wind is cost competitive. Why? Well, if we switched completely to wind energy, new plants would need to be built, a national electric grid to transfer energy from windy areas (mountain west) to the coasts, our transportation system would need drastic changes, home heating systems would need replacement, etc. With respect to solar technology, silicon has a major stronghold in history and manufacturing capacity. New technologies will have to be drastically better to replace silicon for rooftop applications. Are there any environmental issues associated with the use of metal organic frameworks in these types of applications? Metal organic framework synthesis does require the use of organic solvents such as dimethyl formamide, but mechanochemical synthesis of MOFs is an emerging area and can
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The scientific community must solve this challenge for widespread solar energy utilisation eliminate this concern. Beyond that, the environmental concerns come down to the chosen components in the metal organic frameworks and the speciation of these components when the material is disposed of. The development of metal organic frameworks is not yet at a stage to warrant life-cycle analysis. However, the first commercial application of a MOF was recently reported, so perhaps such studies are on the horizon. Do you think it will be possible to potentially combine the various applications of metal organic frameworks in a single device? I firmly believe that through scientific innovation we will be able to integrate the functionality of photosynthesis into a metal organic framework array. The question for me is not if, but when. Truly, that I cannot answer, but it will be a major thrust of my research group for the foreseeable future. Do you think it will ever be possible to perform artificial photosynthesis with similar efficiencies to photosynthesis in plants? It depends on how one defines efficiency. If one simply considers the efficiency as solar photons to chemical fuel yield, the answer is yes. Current technology exists to drive photosynthetic chemistry at much higher efficiencies than plants – near 10%. The issue is that technology comes at a cost – another component of efficiency. Plants in comparison to platinum catalysts and semiconductors are very cheap. The challenge that remains is how to produce the efficiency of photosynthesis at a cost competitive level.
RESEARCH OBJECTIVES Dr Morris’ research focuses on two aspects of solar energy conversion: solar energy storage through artificial photosynthesis and next generation solar cells. FUNDING Department of Energy (DOE) COLLABORATORS Yulia Pushkar, Purdue BIO Amanda Morris’ research education conducted at Penn State University (BS), Johns Hopkins University (PhD), and Princeton University (Postdoctoral) has focused on addressing critical environmental issues with fundamental science. As her publication record shows, Dr Morris is a classicallytrained photo-electrochemist with demonstrated success in utilising various techniques within renewable energy research. CONTACT Dr Amanda J. Morris, Assistant Professor Virginia Tech – College of Science Department of Chemistry 3109 Hahn Hall South Blacksburg, VA 24061 USA E: ajmorris@vt.edu T: +1 540 231 5585 W: http://www.ajmorrisgroup.chem. vt.edu/
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Kinetic descriptions – a mathematical bridge to better understand the world
Mathematics
Professor Eitan Tadmor from the University of Maryland is director of KINet – a unique Mathematics research network that enables collaboration between participants in geographically distinct hubs and nodes. The network of 20+ nodes and more than 50 core participants is making significant contributions to the field of kinetic theory – mathematical description of small fluctuations with applications ranging from quantum chemistry to biology and social sciences.
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hen birds flock together, each individual bird interacts only with those closest to it; it aligns its velocity or its direction with an average velocity of its immediate neighbours. The adjustment that each bird makes involves only small local fluctuations. What we see from the ground, however, is quite different: we see a single mass that moves as one, creating mesmerising patterns. Kinetic descriptions is the mathematical tool which bridges the transition from modelling the small scale at the individual level of each bird, to the large scale realised at the group level of the flock. STRENGTH IN NUMBERS The idea that a sufficiently large number of small local fluctuations are combined to create a larger global impact, can be applied to many different areas. Take cells in the human body, for example. Each cell is acting only in response to its neighbouring cells; if you have a few cells in a petri dish, there is no large-scale outcome. However, the operation of millions of cells in the human body can selforganise to form organs as delicately complex as the eye or systems as wide-ranging as the blood vessel network. The term ‘many body problem’ refers to those configurations in which a global impact will emerge only if a sufficiently large number of interacting individuals, like cells or birds, are involved. TRANSITIONING FROM MICRO TO MACRO The original birthplace of kinetic theories is the emergence of properties of matter from local fluctuations at the molecular level. Take for example the air we breathe. Here, the microscopic fluctuations of air molecules, each
colliding with locally neighbouring molecules, take place on the atomistic scale. But when taking into account their huge number, the global effect of such collisions is realised on the macroscopic scale, as the temperature and density of the air. Kinetic description provides the link between these two scales. In the words of Professor Tadmor – “it is description across scales”. This paradigm of self-organisation is applicable in a broad range of different contexts, from individual molecules and birds to cars or even opinions which self-organise as part of a greater body of material, flock, traffic flow or consensus, through judicious interactions with local neighbours. It is this paradigm that Professor Tadmor has focused on in recent years. THE RULES OF ENGAGEMENT One area where the research focus of Professor Tadmor has led to fascinating, counter-intuitive outcomes is the propagation of opinions. Here, instead of molecules there are individual opinions; instead of collisions there is an exchange of ideas, where each individual is influenced by the opinion of its closest neighbours. Applying the methodology of kinetic descriptions to social sciences is still a fairly young discipline, but it can give invaluable insight into the way we organise ourselves. And it is here that Professor Tadmor emphasises the importance of rules of engagement: namely, how the local fluctuations due to neighbouring opinions have a global impact on the overall outcome in forming parties, reaching consensus, etc. BIRDS OF A FEATHER FLOCK TOGETHER Generally, we tend to gravitate towards those with similar opinions to our own, whether this is in the context of political parties or playground music preferences. In contrast,
Applying the methodology of kinetic descriptions to social sciences is still a fairly young discipline, but it can give invaluable insight into the way we organise ourselves 63
Mathematics
Figure 1 (Heterophilious vs. homophilious dynamics). Large-time behaviour of Hegselmann-Krause model with opinions distributed between 0 and 10 at t=0.
Left figure: homophilious dynamics. Interaction between any two opinions takes place only if the difference of their opinions is less than 1 (drawn by ϕ on top right). It yields four distinct parties from time t=5 thereafter.
those with significantly different opinions to ours have much less influence. In fact, we are more likely to dismiss their opinion entirely and stick to our own. Aligning with those you are already closest to is called ‘homophilious’ interaction. OPPOSITES ATTRACT Imagine, for a moment, a different scenario: rather than dismissing the opinions that are furthest from your own, you pay more attention to them, more than those opinions closest to yours. This is ‘heterophilious’ interaction. Contemplate the two different rules of engagement, homophilious and heterophilious interactions, and examine their global impact. Here comes the ‘counterintuitive’ part – according to Professor Tadmor, it is the heterophilious interaction of opinions which is more likely to produce consensus. But why? After all, the expectation is that interacting with those whose opinions correlate to yours is more likely to bring about agreement. The answer lies in the communication among individual opinions. Homophilious interactions tend to cluster those that think alike together, and consequently, they tend to separate into different groups or parties of distinctly polarised opinions which lack the ability to influence each other. Communication therefore breaks down. However, placing a greater emphasis on alignment with those
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Right figure: heterophilious dynamics. Same as before, but with LESS attention given to those which are ‘close’ in their opinion (if distance between two opinions is less than 0.7 then they take 1/10 of the importance of those who are farther away, with distance between 0.7 and 1 drawn by ϕ on top right. Paying more attention to those who are different, leads to the emergence of consensus at time t=35.
further away is more likely to keep the lines of communication among individual opinions open, so that the many fluctuations of local compromises on the individual scale add up and, counterintuitively, consensus emerges on the large scale. As Professor Tadmor explains, while in the homophilious case a disconnect could arise between polarised groups, “heterophilious dynamics prevents the scenario of dysconnectivity”. THE EMERGENCE OF CONSENSUS This emergence of consensus, as Professor Tadmor emphasises, is not a certainty but a ‘more likely’ possibility. In fact, the theory of kinetic descriptions has an essential probabilistic element. When considering the interaction of the ‘many body problem’ or engagement of many individual birds, cars or opinions, one has to contemplate many, many more possible interactions. Kinetic descriptions deal with the most likely outcome out of this huge ensemble of possible configurations. Kinetic description governs
the transition from the microscopic level to the human, macroscopic level, not in terms of certainty of the outcome but in terms of the probability of the most likely final outcome. KI-NET The theory of kinetic descriptions has a long history, branching out from James Clerk Maxwell’s work on statistical mechanics in the mid-19th century. The body of work that has developed since then has been remarkably successful at predicting large-scale phenomena across natural, life, and more recently, social sciences. This is now being added to by the work at KI-Net. This research institute, headed by Professor Tadmor, is unique in its structure. Rather than being based at a single institution, its members are spread across sites, mainly in the US but also in Europe. Researchers outside of the network also collaborate on each project so the crowd of hundreds of scientists involved with KI-Net activities is even greater than the currently expanding 50 core participants.
With applications ranging from propagation of opinions to tumour formation and traffic monitoring, the mathematical theory of kinetic descriptions encompasses a broad range of applications www.researchfeatures.com
Detail
Kinetic description can be used to describe the flocking of birds
Faced with the complexities of directing a large network that is not based in a physical institute, Professor Tadmor and his IT team in the Center for Scientific Computation and Mathematical Modelling (CSCAMM) at the University of Maryland created an online platform which enables the network to run a decentralised yet synchronised series of activities. Participants can add information, set up requests and disseminate information about projects via the dedicated KI-Net online platform. At the same time, the three main hubs involved in the network (University of Maryland; University of Texas-Austin; University of Wisconsin-Madison) can then allocate finance in response. Crucially, however, the platform is also a base for KI-Net core participants to communicate, exchange knowledge, collaborate and develop links with other researchers. Much like its research focus on kinetic descriptions, KI-Net itself is a platform that provides an additional level of communication between individual researchers, whose interactions promote the larger body of work on this area. Perhaps the most important product of KI-Net, says Professor Tadmor, is creating the sense of community. A key example is the network‘s focus on the support of junior researchers. The KI-Net annual Young Researchers Workshops (YRW) have become a key date in the calendar, expanding each year. Unlike a usual conference, the focus here is solely on junior, pre-tenure researchers who make up an exclusive group of participants and invited speakers. The KI-Net YRWs have proven enormously beneficial, not only in creating a community of talented junior researchers, but also to the institutions involved, looking to attract top talent.
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RESEARCH OBJECTIVES Professor Tadmor has been involved in ground-breaking work on the theory and computation of differential equations which involve high-resolution schemes for shock waves and kinetic formulation of conservation laws. He introduced novel ideas of multi-scale hierarchical descriptions of images, and he is currently leading an interdisciplinary programme on self-organised dynamics with applications to flocking and propagation of opinions.
FLYING HIGH Professor Tadmor has had a distinguished career as a leading figure heading several research institutes (including Sackler’s in Tel-Aviv University, IPAM at UCLA and CSCAMM in Maryland) of which KI-Net is the most recent. He highlights the importance of collaborative work, stating that he feels “privileged” when the work he does has an impact, and his ideas are well-received in the community. As the recipient of the 2015 Peter Henrici prize for “original contributions to applied analysis and numerical analysis”, it is clear that his voice carries a considerable weight. UNIVERSAL LANGUAGE Professor Tadmor speaks with evident passion for the subject of Maths: “Maths is a language. There is something very warming and welcoming when you meet other colleagues across the world, and you feel almost at home because you know how to speak this universal language of Maths with its many dialects”. With applications ranging from the propagation of opinions to tumour formation and traffic monitoring, the mathematical theory of kinetic descriptions encompasses a broad range of applications. Professor Tadmor is convinced of the importance and value of continued work in the area of kinetic descriptions: “It took many years to develop this paradigm, but it is far from being complete. There are many questions which are yet to be addressed; and that's exactly what we do in the KI-Net – our KI-Net community is trying to build higher, reach farther and dig deeper in the theory of kinetic descriptions.”
FUNDING National Science Foundation (NSF) COLLABORATORS As the KI-Net Director leading its main hub at the University of Maryland, Professor Tadmor is collaborating with Professor Irene Gamba and Professor Shi Jin who, respectively, lead the two other KI-Net hubs at the University of Austin-Texas and University of MadisonWisconsin. BIO Professor Tadmor received his BSc, MSc and PhD in Mathematical Sciences from Tel-Aviv University in 1973, 1975 and 1979, respectively. Following his post-doc at Caltech, he returned to Tel-Aviv University, where he chaired the Department of Applied Mathematics. In 1995 he moved to UCLA where he co-founded the Institute for Pure and Applied Mathematics (IPAM), before joining the University of Maryland in 2002, heading its Center for Scientific Computation and Mathematical Modelling (CSCAMM), 2002–2016. This year, Prof Tadmor spends a sabbatical at ETH-Zurich as a Senior Fellow at the Institute for Theoretical Studies. CONTACT Professor Eitan Tadmor Distinguished University Professor CSCAMM, CSIC Bldg. 406 University of Maryland College Park MD 20742 USA T: +1 301 405 0648 W: http://www.cscamm.umd.edu/tadmor
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Thought Leadership
E-MRS: Rewarding collaborative materials research Dr Luisa Torsi is the President of the European Materials Research Society – an interdisciplinary organisation which has been at the centre of materials science since its inception back in 1983. She recently met with us at Research Features to discuss her organisation’s current areas of research, outlining why rewarding researchers of all ages is so important and why more needs to be done to support women in science.
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he Colosseum of Rome, the Leaning Tower of Pisa, Stonehenge. Ensuring the longevity of magnificent historic structures like these, without compromising their historic and cultural integrity, is just one of the many areas that scientists from the European Materials Research Society are currently looking into – such is the expansive nature of their field. Dr Luisa Torsi, the President of the European Materials Research Society, recently spoke with us at Research Features about this and her organisation’s other areas of research in more detail, including an exciting X-ray system. How would you describe your role as President of the European Materials Research Society (E-MRS) and what kind of responsibilities do you have? Technically the president of the E-MRS is the president of the Executive Committee (Ex. Comm), the body that is in charge of all aspects of the life and work of the society. It is the Ex. Comm’s duty to make sure that the society contributes to the advancement of the science and technology of new materials, through consultation, cooperation and the exchange of information between scientists and engineers. The Ex. Comm also identifies priority areas for European research and provides advice for European research programmes. This is an interesting role in a highly dynamic society. The E-MRS differs from many
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single-discipline professional societies, as it encourages scientists, engineers and research managers to exchange information on an interdisciplinary platform. The society also recognises professional and technical excellence by presenting awards for achievement, from student to senior scientist level. As part of the International Union of Materials Research Societies (IUMRS), the E-MRS enjoys and benefits from very close relationships with other materials research organisations elsewhere in Europe and around the world. E-MRS is currently running multiple projects in different areas. What are the key research focuses for the organisation over the next two years? E-MRS has been involved in a number of European projects on several themes, ranging from using CO2 as a raw material for energy storage, to materials for cultural heritage. One particular venture I’d like to mention is the i-FLEXIS project. i-FLEXIS is a newly developed X-ray sensor system, which uses crystals to sense the presence of X-rays. Innovative in design, this reliable and low-cost device has many potential areas of application, including radiography, radiology and airport security. Current X-ray detecting tools tend to be bulky, rigid, costly and nonenergy efficient, whereas i-FLEXIS is both flexible and robust, and offers an affordable, environmentally-friendly alternative. Quite different, but equally strategically relevant, is the HERACLES project. The aim of this project is to develop innovative solutions to reinforce the resilience of cultural heritage sites,
structures and artefacts against the effects of climate change and natural hazards. Part of the HERACLES remit is to design solutions which take into account the meaningfulness of these cultural sites for people, and to respect their historic and cultural integrity. How big an influence has E-MRS had on materials science since it was first established in 1983? Are there any achievements that really stand out for you? I would say the E-MRS has definitely set the standard for fostering and disseminating materials research in Europe. It was established in 1983, thanks to Professor Paul Siffert and other scientists.
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E-MRS spring meeting 2016, in Lille, France
The E-MRS differs from many single-discipline professional societies, as it encourages scientists, engineers and research managers to exchange information on an interdisciplinary platform www.researchfeatures.com
At that time, before the European Union started to support research and development, materials scientists were already advocating a pan-European approach. The E-MRS’s main achievement over the years has been supporting the development of scientists and engineers, not only from academia, but also from the private sector. This has been vital for the development of materials science as an interdisciplinary topic within Europe. Every year E-MRS organises a spring conference. Could you tell us a bit more about this? How important is it for the materials research community? The E-MRS spring meeting is held every
year in May or June and features a diverse selection of topical symposia. Our aim is to cover a wide range of topics, whilst also providing an opportunity for the deepening of discussions in key fields to occur. This is the reason why the number of parallel symposia has never grown too large. Nonetheless, the number of attendees has been always reasonably high. Internationally significant, the conference is the largest of its kind in Europe, with about 2,500 attendees every year. Those who present symposia at the meeting often publish their own findings, documenting the latest experimental and theoretical developments
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in material science. One significant aspect of the 2017 meeting is that this year we will be returning to Strasbourg which, as well as being the seat of the European Parliament, we consider to be the E-MRS’s home. E-MRS also organises a fall conference – how is this different to the spring conference? The fall meeting, held in the elegant Technical University of Warsaw, is steadily expanding, with attendance figures now reaching nearly 1,500. It has an excellent programme which features the latest developments in the topics selected by the conference chairs. The main differences reside in the recognition awards that are presented in the two main conferences. The Warsaw meeting is characterised by the awarding of the prestigious Jan Czochralski award, named after one of the renowned Polish scientists. Previous recipients of the award include Professor Federico Capasso and Professor Mildred Dresselhaus. Besides the two conferences, each year E-MRS organises, coorganises, sponsors or co-sponsors numerous scientific events and meetings. Collaboration and communication are obviously key elements to the success of E-MRS. How did the European Materials Forum (EMF) come about? What are its main aims? And what else does E-MRS do to foster scientific collaboration? The European Materials Forum, EMF, was initially launched in 2004, when a number of scientific societies and organisations (including the E-MRS) decided to combine their efforts and shared interest in the debate about materials science in Europe. They were also interested in stimulating the involvement of the scientific community in Europe, not only through an active participation in the debate, but also by generating strong contacts between research and industry. The long-term agenda of the EMF is the promotion of scientific and technological development in Europe in the field of materials science and technology. Particularly relevant is the recognition of the importance of the objectives defined by the Lisbon and Barcelona EU Summits. The activities of the EMF include an open exchange of ideas and information, plus the preparation of statements on European materials science policy issues. EMF has already organised several meetings and more than 80 materials societies have supported these conferences. From a more personal perspective, your research has spanned multiple disciplines. How important has cross-speciality
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collaboration been to your work? Multi-disciplinarity is a constant in my career. My masters degree is in physics, while my PhD is in chemistry, and I’ve always worked at the interface between the two. It is challenging, but very interesting, and I see materials science as the natural discipline in which to develop my research activities. In 2010 you became the first woman to receive the Heinrich Emanuel Merck Prize for Analytical Sciences. This was the first time it was awarded to a woman and to an Italian scientist. How does it feel to win such an award? Do you think enough is being done to encourage more women into the area of materials science? The winning of the Merck prize was a real milestone in my career. It felt amazing to receive such recognition for my work. I was given the award for my work on organic semi-
conducting chemical sensors based on organic field-effect transistors. Such components make it possible to perform highly sensitive analytical measurements of chiral substances. Besides being a very difficult bench-test for sensors, chiral substances are important as they are responsible for many biological effects in enzymes, antibodies or other molecular systems. As you mention, the prize marked the first time the award was given to a woman and to a scientist in Italy. For more than 20 years, the Heinrich Emanuel Merck Award has been recognising scientists under the age of 45 whose work focuses on new methods in chemical analysis and the deployment of applications aimed at improving the quality of human life, in fields such as environmental protection, life sciences or the biosciences.
My masters degree is in physics, while my PhD is in chemistry and I’ve always worked at the interface between the two www.researchfeatures.com
The problem of the very low presence of women in science, particularly when it comes to apical positions, is a huge one and it is far from being solved. The statistics are very clear on this. I believe that not enough is being done to solve this problem and, sadly, it is the same all over Europe and in the USA. I think the promotion of positive role models is a really important way of encouraging younger female students to consider not only jobs in science and technology, but also those of an apical position. How do you see the landscape of materials science research changing over the next ten years? What strategies will the E-MRS be putting in place to facilitate future developments? E-MRS will keep fostering the advancement of materials science as a key field for the development of technologies, with applications ranging from healthcare to energy. We will do this though the organisation of large meetings, as well as by providing a space for the development of activities and forums between academia, industry and policy makers to take place.
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Dr Luisa Torsi speaking at the E-MRS spring conference
Another key activity of the E-MRS is dissemination and recently, thanks to the efforts of Professor Rodrigo Martins, a toptier interdisciplinary platform for scientists to share and promote 2D materials research and applications has been established. E-MRS has also co-founded a new onlineonly, open access journal: npj 2D Materials and Applications. The publication is part of the Nature Partner Journals series, published in partnership with the Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa (FCT Nova) with the support of the E-MRS.
Contact European Materials Research Society 23 Rue du Loess BP 20 - 67037 Strasbourg Cedex 02 France E: emrs@european-mrs.com W: www.european-mrs.com
• To find out more information about the European Material Research Society’s events and meetings, please visit their website at www.european-mrs.com.
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Physics
The physics of extreme matter: how did the universe begin?
What happens to matter when you heat it to more than a trillion degrees? Dr Jinfeng Liao and his team at Indiana University are exploring the properties of an exotic form of matter, known as a quarkgluon plasma, that only exists at such extreme temperatures. In the first few microseconds (that is, a few millionths of a second) after the Big Bang, the universe was thought to be composed entirely of such quark-gluon plasmas and, by re-creating them in the lab today, Dr Liao is exploring what they can tell us about the one fundamental force, the strong nuclear force, of the universe.
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n our everyday experience, there are three main phases of matter: solids, liquids and gases. Most materials that are solid at room temperature, if you heat them enough, will become liquids and eventually gases. However, at very high temperatures, new, more exotic states of matter start to occur. One such state of matter is known as a quark-gluon plasma, which is thought to be the first form of matter that made up the entire universe in just the first few microseconds after the Big Bang.
Heavy Ion Collider (RHIC), to discover the underlying patterns in the strong nuclear force that dictates the visible matter world of our universe.
Although it is commonly said that atoms are the smallest of matter, this is untrue. Atoms are composed of subatomic particles, called protons, electrons and neutrons. Neutrons and protons are relatively heavy, in comparison to electrons, but are further divisible into even smaller units known as quarks. The quarks are held together by a ‘force carrying’ particle, known as a gluon, that essentially sticks all the quarks together to make larger particles. It is these quarks and gluons that make up the plasmas that existed in the early moments of the universe.
To do this, it is necessary to accelerate the particles of interest along many kilometres of beam lines so that they travel almost as fast as light rays. The particles are then smashed into each other with energies sufficient to generate the temperatures needed to form the quark-gluon plasmas. A series of sophisticated detectors are then used to watch how these plasmas behave, providing insights into the nature of matter in these extreme conditions.
Dr Jinfeng Liao and his team at Indiana University are interested in exploring the properties of these quark-gluon plasmas to better understand the fundamental structure of matter. It is now possible to recreate this primordial cosmic matter in the laboratory and Dr Liao has been investigating the results of such experiments, performed at places like the Large Hadron Collider (LHC) at CERN and Brookhaven National Lab’s Relativistic
LITTLE BANG MACHINES In quark-gluon plasmas, the temperatures are in excess of a trillion degrees. These temperatures are nearly 100,000 times hotter than the centre of the sun, so how can the experimental colleagues of Dr Liao at LHC and RHIC generate similar conditions in the laboratory?
NEW PHASE OF MATTER This new phase of matter, the quarkgluon plasmas, has many interesting properties. It behaves like a nearly perfect fluid and has extreme “stopping” power to an energetic penetrating particle. Perhaps more interestingly, such unusual properties can help physicists to develop a better understanding of how quantum chromodynamics (QCD) works in nature. QCD is a theory that describes the strong interactions between the quarks and gluons found in these plasmas. Furthermore, QCD
Quarks and gluons make up the primordially hot plasma that existed in the early moments of the universe
Physics
holds the key to understanding exactly how the building blocks of atoms and molecules, protons and neutrons, are constructed from the more basic quarks and gluons and exhibit their observed properties. This same theory is also responsible for understanding the phenomena that occur in the particle collision experiments performed in places like the LHC and RHIC. While the conditions of the modern universe may be very different to its early days, Dr Liao is interested in further exploring the nature of quark-gluon interactions by studying the epoch matter of quark-gluon plasma. In ‘normal’ states of matter, the quarks and gluons are deeply bound inside protons and neutrons and cannot be directly accessed. But in high-temperature plasma conditions the quarks and gluons become freed to roam around – thus offering an otherwise unavailable environment for manifesting the strong interaction between them. A lot has been learned in the past decade about the behaviours of the quarkgluon plasma, nevertheless it remains highly challenging to transfer our understanding of the quark-gluon plasma to help unravel the mysteries of QCD and its predictive capabilities – something Dr Liao is hoping to address through his research. AN ANOMALOUS UNIVERSE Lately, Dr Liao has been investigating one particularly interesting facet of quark-gluon plasma. A common theme in subatomic physics is the idea of symmetry, which encodes the many secretive patterns of the physical laws. The idea of symmetry has helped predict many of the particles that have eventually been found at the LHC and other similar particle accelerators. However, the physics of symmetry is more versatile than the usual conception: besides rigorous symmetries, broken symmetries also play vital roles in physical theories. Dr Liao is particularly interested in one intriguing case, known as the chiral anomaly. This refers to a kind of symmetry called
A view of one of the first full-energy collisions between gold ions at Brookhaven National Laboratory's Relativistic Heavy Ion Collider. The tracks indicate the paths taken by thousands of subatomic particles produced in the collisions as they pass through the STAR Time Projection Chamber, a large, 3D digital camera. Credit: Image courtesy of Brookhaven National Laboratory.
chiral symmetry for a category of particles known as chiral fermions. Such a symmetry, while holding in classical mechanics, gets broken in the quantum mechanical description. Physicists, Dr Liao included, have been very curious about the general consequences of the chiral anomaly for macroscopic properties of matter, with quark-gluon plasma as a particular example.
“Chiral Magnetic Effect”. This effect is the unique signature of such a chiral anomaly, as first advocated by Dr Dmitri Kharzeev, a professor at Stony Brook University and Brookhaven National Laboratory. Dr Liao has been working to make predictions for how this process may occur quantitatively to aid the experimentalists’ search for this effect in heavy-ion collisions.
One category of potentially observable effects is known as anomalous chiral transport, with a notable example called
Finding this effect will be a milestone in understanding the fundamental physics of chiral anomaly and quantum matter. Ultimately, understanding it will aid understanding of the processes that are responsible for the early cosmic magnetic fields as well as astrophysical matter in neutron stars and supernovae. With many of the theoretical studies developed by Dr Liao and his team, it is possible that we are getting very close to an answer to whether such effects can be observed in future experiments, providing a new insight into the forces that glue our universe together.
Dr Jinfeng Liao and his team at Indiana University are interested in exploring the properties of the quark-gluon plasma to better understand the fundamental structure of matter 72
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Detail What is a quark-gluon plasma? A quark-gluon plasma is a new phase of matter at a temperature of about a trillion degrees or higher. Different from normal materials that are made of such building blocks as protons and neutrons where quarks and gluons are deeply hidden inside, a quark-gluon plasma is directly made of the quarks and gluons. On the other hand, it was also the old phase of matter in the early universe shortly after the Big Bang. Are there any situations today where quark-gluon plasmas naturally occur? Today the quark-gluon plasma can be reborn in the laboratory by “atom smashers”, namely the high energy colliders such as the Large Hadron Collider in Europe and the Relativistic Heavy Ion Collider in the US. These experiments create the highest manmade temperature in the “hot spot” created by two colliding particles where a quark-gluon plasma occurs. What are the possible applications of quantum chromodynamics? Quantum chromodynamics is the underlying basic theory for describing all nuclear forces and nuclear phenomena. It lays the foundation for numerous applications from energy generation in
nuclear power plants to medical imaging via magnetic resonance imaging (MRI). Do you think it is likely that anomalous chiral transport will be observed soon? The anomalous chiral transport is currently predicted to occur in two possible laboratory systems. It has been observed in condensed matter materials called Dirac and Weyl semimetals. It has been enthusiastically searched for in the quark-gluon plasma with positive hints. Deliberately designed heavy ion collision experiments, dedicated to the search of such an effect, has been planned for the next couple of years and will very likely lead to a definitive answer. What do you think will be the future of heavy-ion collision experiments? Active experimental programmes at the LHC and RHIC have been planned for the next decade, with an array of exciting scientific goals and great potential for important discoveries, such as the search for anomalous chiral transport. Other examples include the possibility of finding, for the first time, a distinguished phenomenon known as the critical point for nuclear matter.
RESEARCH OBJECTIVES Dr Liao’s research focuses on the basic theory of quark and gluon matter, known as quantum chromodynamics (QCD), and the phenomenology of high energy heavy ion collisions. FUNDING National Science Foundation (NSF) RESEARCH TEAM MEMBERS Shuzhe Shi and Miguel Angel Lopez Ruiz (PhD students), and Yin Jiang (postdoctoral researcher) BIO Dr Liao studied for a BS and MS in Physics at Tsinghua University in China before undertaking a PhD in Nuclear Theory at Stony Brook University, USA. From there, he worked at the Lawrence Berkeley National Laboratory and Brookhaven National Laboratory before, in 2011, becoming an Assistant Professor and very recently an Associate Professor at Indiana University. CONTACT Dr Jinfeng Liao Associate Professor Physics Department Indiana University 727 E 3RD ST Bloomington Indiana 47405 USA E: liaoji@indiana.edu T: +1-8128567796 W: www.indiana.edu/~iubphys/faculty/ liaoji.shtml
The “Extreme Matter” research team, on the balcony at the Center for Exploration of Energy and Matter of Indiana University: (left to right) Yin Jiang, Miguel Angel Lopez Ruiz, Jinfeng Liao and Shuzhe Shi
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Astrophysics
The aurora australis over the Amundsen-Scott South Pole Station Credit: Patrick Cullis, NSF
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IceCube: experimental particle astrophysics with high energy neutrinos Dr Joanna Kiryluk is an assistant Professor of Physics at Stony Brook University, who for the last ten years has dedicated her research to studying the mysterious neutrinos: massless elementary particles whose energies far exceed those produced by accelerator beams. The aim of her current project at IceCube, the South Pole neutrino observatory, is to utilise electron and tau neutrino detection in order to target and investigate the energy and flavour characteristics of the flux of highly energetic neutrinos. Or, in other words, Dr Kiryluk’s objective is to identify and understand the most powerful cosmic accelerators in the Universe.
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ne of the most intriguing and challenging issues in astrophysics involves the investigation of astrophysical sources that can subsequently provide scientists with a greater insight regarding the enigmatic origin of the highest energy particles in nature – neutrinos. NEUTRINOS: AN INTRODUCTION Neutrinos are created by violent astrophysical events (i.e., exploding stars [supernovas] or gamma ray bursts) and are critical to the make-up of the universe. Although very similar to electrons, neutrinos are not electrically charged, and so remain unaffected by electromagnetic forces; instead, they are mildly affected by gravity and by subatomic weak forces. Neutrinos can therefore travel great distances through cosmic matter and for this reason are known as cosmic messengers – key elements in understanding the powerful cosmic accelerators in our Universe. Owing to their very small mass and their lack of charge, neutrinos (unlike photons) are capable of escaping from very dense
astronomical environments. So, in order to investigate cosmic ray acceleration, scientists rely solely on neutrinos to act as tracers of such environments. Imagine the broken clay pieces that are revealed by archaeologists to provide distinct and unique information regarding a past era – neutrinos act in this way for the era that formed the origins of sub-atomic particles. Essentially, there are three types, or ‘flavours’, of neutrinos that have no net electric charge, where each one of them is connected to a corresponding charged particle. These comprise the electron neutrinos (ve), which were discovered in 1956, the muon neutrinos (vμ), which were discovered in 1962, and the tau neutrinos (vτ), which were discovered in 2000. Neutrinos of all flavours form the core of the so-called IceCube project – a project that Dr Kiryluk has been an integral member of since 2007. THE ICECUBE PROJECT The IceCube project is a particle detector located below the surface of the South Pole. It’s target is to glean information from neutrinos, particularly due to the ability
Neutrinos are created by violent astrophysical events (i.e., exploding stars [supernovas] or gamma ray bursts) and are critical to the make-up of the universe www.researchfeatures.com
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Astrophysics
Above: Dr Joanna Kiryluk - Credit: Stony Brook University Right: Neutrino event display - Credit: IceCube
of these particles to travel long distances without being disturbed by prevailing cosmic interactions. IceCube is the first gigaton neutrino detector ever built, with its primary function aimed at searching for neutrinos in the most violent astrophysical sources, including cataclysmic phenomena, such as black holes and neutron stars. Currently, there is no direct method of observing such particles. Instead, they can be indirectly observed as a result of their interactions with the ice and the subsequent production of secondary electrically charged particles. These secondary charged particles can travel much faster than light in a dielectric medium such as ice, and hence they emit the so-called Cherenkov light. The IceCube, with its sensors, collects this generated light and subsequently digitises it, allowing scientists to
gain a greater insight into its initial direction, energy and origins. Since 2012, this project has announced new observations regarding high-energy neutrinos that originate beyond our solar system. DR KIRYLUK’S WORK AT THE ICECUBE There are currently two principal aims for Dr Kiryluk’s research. The first one involves determining the flux of electron and tau neutrinos. This will, in turn, allow scientists to gain a greater insight into the diffuse astrophysical electron and tau neutrino energy spectrum, and their characteristics including their flavour composition down to single (individual) neutrino flavours. In other words, Dr Kiryluk’s work intends to unravel the neutrinos’ production mechanisms and acceleration mechanisms and the
Dr Kiryluk’s work intends to unravel the neutrinos’ production mechanisms, nuclear composition, and acceleration mechanisms and the properties of the neutrino sources 76
properties of the neutrino sources. This, in turn, will allow unique observations and suggestions to be made in relation to the origin of cosmic neutrinos and of ultra-highenergy cosmic rays. Her second research aim involves the search for anisotropy, which will provide solid evidence for a galactic and an extragalactic origin of the recently discovered astrophysical neutrinos. In fact, according to the current research performed in the IceCube, if the magnitude of anisotropy is found to be small, this will suggest that practically all cosmic neutrino radiation has an extragalactic origin. Conclusively, Dr Kiryluk’s work at the IceCube has every potential to provide scientists with a greater insight that will provoke a critical impact on neutrino astrophysics by, simultaneously, offering ample potential for continued discovery. As Dr Kiryluk puts it herself: “With this study, we are able to present the first comprehensive characterisation of the astrophysical electron and tau neutrino flux at IceCube.”
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Detail How exactly can you determine the diffuse flux of highly energetic neutrinos? Data collected with the IceCube experiment consist of a mixture of astrophysical neutrinos, signal, as well as cosmic ray-induced atmospherical backgrounds. In the analysis, we develop methods to reject the dominant atmospheric background contributions from our data, while keeping the neutrino signals of interest. Following this selection, we sort the remaining data in intervals of angle and energy. For each interval we evaluate the expected background using Monte Carlo techniques. An excess observed in the data over the expected background is our measurement of the flux of astrophysical neutrinos. We can describe the energy dependence of the flux of astrophysical neutrinos with a single power law form. We use maximum likelihood fitting techniques to extract the overall size, or normalisation, of the astrophysical neutrino flux and the energy slope, or spectral index, from the data. Future data will make it possible to investigate more intricate energy dependences, beyond a single power law. Why is IceCube located where it is and not, for example, in space – much like the Hubble telescope? Neutrinos are elementary particles that interact weakly. Their detection requires large and massive instruments. To detect high-energy astrophysical neutrinos, instruments with a volume of one cubic kilometre or larger are needed. This is the reason why neutrino telescopes use ice (Antarctica) or water (Mediterranean Sea, Lake Baikal) as part of the instrument. It is currently not practical to construct such detectors in space. The determination and verification of anisotropy would mean that an important part of the cosmic neutrinos originates outside our galaxy. What is the significance of this discovery? The astrophysical neutrinos that have been observed by IceCube so far are isotropically distributed in the sky. This
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I feel fortunate to be able to pursue science, do so with IceCube, and contribute to its science goals means that the data strongly favour extragalactic origins for these neutrinos. Any indication of a neutrino flux anisotropy between the Northern and Southern skies would point to the existence of a galactic component, and would mean that the energy spectrum will have a rich structure. The characterisation of the galactic flux of neutrinos, if or when it is observed, will enable new studies of various models of possible galactic sources, such as the Galactic Halo, Sagittarius A* or Fermi Bubbles as well as of the diffuse emission from galactic cosmic rays. Why have you selected this project, a project that you have been working with over the last ten years? I am fascinated by high-energy phenomena, nuclear physics, and astro particle physics. IceCube is an experiment that speaks to the imagination, requiring the combined expertise from many disciplines to succeed. Neutrino astronomy offers tremendous potential for discovery, despite the experimental challenges that have required development over generations. I feel fortunate to be able to pursue science, do so with IceCube, and contribute to its science goals. What are your objectives in terms of time scale, in order to accomplish the targets of your research? Over the next several years, we aim to observe a sufficiently large number of astrophysical neutrinos to be able to characterise their energy spectrum and learn about the physical mechanisms that are at the origin of the most energetic processes in the universe.
RESEARCH OBJECTIVES Dr Kiryluk’s research focuses on studying subatomic particles called neutrinos. Her latest work looks to target the energy and flavour characteristics of a diffuse flux of highly energetic neutrinos. FUNDING National Science Foundation (NSF) COLLABORATORS • IceCube (www.icecube.wisc.edu/ collaboration/icecube) • National Science Foundation (www.nsf. gov) • Department of Physics and Astronomy, Stony Brook University (www.physics. sunysb.edu/Physics/) • Women in Science and Engineering programme at Stony Brook University (www.stonybrook.edu/wise/) BIO Dr Kiryluk is an assistant professor in the Department of Physics and Astronomy at Stony Brook University. She obtained her PhD in Physics from Warsaw University, Poland, and has worked at the University of California Los Angeles, the Massachusetts Institute of Technology, and Lawrence Berkeley National Laboratory. CONTACT Dr Joanna Kiryluk Assistant Professor of Physics Department of Physics and Astronomy Stony Brook University Stony Brook, NY 11794-3800 USA E: joanna.kiryluk@stonybrook.edu T: +1 (631) 632 7734 W: http://skipper.physics.sunysb. edu/~joanna/
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Galactic nucleosynthesis: the onset of element production in our galaxy
"Kepler's supernova" was the last exploding supernova seen in our Milky Way galaxy - Johannes Kepler, among others, observed it with the naked eye in 1604
Astronomy
In an extended study investigating how elements are formed and galaxies chemically evolve, Dr Christopher Sneden from the University of Texas, along with his team, look at stars within our own galaxy for vital clues. There are many diverse populations of stars located throughout the galaxy, from the galactic centre and spiral arms, through to a diffuse, random spread of stellar objects in an area that cocoons the Milky Way, called the galactic halo. Dr Sneden’s research specifically concentrates on ancient, metal-poor halo objects to discover how primordial elements, such as hydrogen and helium, grow to form heavier elements that populate our surroundings.
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e are all aware of the range of substances that makes up the periodic table. From hydrogen, the lightest, most abundant substance in the universe, through to commonly used elements such as copper, iron and uranium. All are familiar, but how are they produced? Apart from hydrogen, helium and lithium, which together make up the three lightest elements forged during the big bang, nearly all elements in the periodic table, known as metals, are forged in nuclear fusion processes throughout a star’s lifetime. This ongoing chemical evolution is what Dr Sneden and his team have dedicated their research to, with particular attention being paid to metal-poor halo objects. This is critical to the research programme, as these ancient objects act as an intermediate source of information linking past stellar activity with current chemical abundancies.
unsustainable and inevitably leads to a core collapse supernova. During the following high energy explosion, as the star obliterates, heavier elements are formed via a process of neutron capture. For this reason, iron and neutron capture are important players within nucleosynthesis, and are elements Dr Sneden pays particular attention to within his research. NEUTRON CAPTURE AS A PATHWAY TO HEAVIER ELEMENTS Due to core reactions becoming endothermic once iron has formed, all heavier elements in the periodic table are formed during a star’s post main-sequence phase or violent supernovae events. Neutron capture is split between two time-variant mechanisms, called the slow (s) and rapid (r) processes.
S-PROCESS The s-process occurs mainly in stars that During a star’s lengthy participation on the range in size from 1 to 8 solar masses. When galactic stage it will go through various hydrogen to helium reactions (hydrogen phases of chemical evolution as lighter burning) cease to be the dominant source of elements, such as hydrogen, fuse to nuclear fusion within a stellar core, the Helium eventually form iron. Once iron is star expands and moves into the Carbon formed within a stellar core the red giant phase of evolution. Oxygen Neon end of its life is imminent. This particular period sees nesium Mag Once this stage has hydrogen burning continue, c Sili on been reached reactions although in a shell Iron in the core become formation enclosing the Core endothermic, meaning core. Helium burning now Cal m ci u more energy is put in to becomes the star’s primary fusion processes than is fusion source in the dense released. This situation is central region, with helium
During a star’s lengthy participation on the galactic stage it will go through various phases of chemical evolution as lighter elements, such as hydrogen, fuse to eventually form iron 79
Astronomy
moving up in the atomic weight scale to form carbon – the next producible element in nucleosynthesis. It is this particular area that Dr Sneden has targeted for exploration, as carbon is by far the main by-product of s-process reactions within the core and any surrounding envelopes. During this stage neutrons are captured by atomic nuclei in the interior stellar fusion zones. Due to their neutral charge this can occur relatively easily. Once a neutron has been captured it can then go through a beta-minus decay, where the neutron decays under the weak nuclear force into a proton to increase the atomic number and form heavier elements. This is known as the 'slow' process because the neutron capture takes a relatively long time compared to the beta decay processes. R-PROCESS In stark contrast, the r-process occurs in very different circumstances and timescales. Although the nuclear processes are the same in principle, neutron capture is realised during violent supernovae events of massive stars greater than about 8 solar masses. Once iron is produced deep within the interior, core-collapse is triggered. The following explosion causes the release of an extreme number of free neutrons, which are then rapidly captured by existing atoms within the debris. Time per reaction is believed to be in seconds rather than thousands of years, therefore heavier elements are produced very quickly. Dr Sneden points out that many ancient, metal-poor stars within the halo show greatly enhanced r-process elements, which he states were produced by high-mass, rapidly evolving stars that existed prior to the formation of any halo stars we observe today. HOW OLD IS THE MILKY WAY? As with any form of research, alternative verification methods are always sought to confirm a theory. Using a distance-independent process called nucleocosmochronometry, Dr Sneden’s team have also been able to provide, utilising their research, an alternative method of ageing the Milky Way. Utilising observed radioactive
Light echo around V838 Monocerotis
isotopes, such as thorium and uranium, age constraints on the galaxy, and subsequently the universe, have been obtained. When compared to alternative estimates already calculated from a diverse number of sources (from thorium/uranium ratios in meteorites to satellite and ground-based sky surveys) the new method provides a galactic age of 12–14 billion years. As Dr Sneden states: ‘Nucleocosmochronology offers promise as an independent dating technique. The chronometric results are generally in agreement with other age estimates such as globular cluster ages and cosmological age estimates.’
The vast majority of elements in the periodic table, known as metals, are forged in nuclear fusion processes throughout a star’s lifetime 80
FUTURE ADVANCES To date, research has advanced well. In his recent paper investigating iron group elements within the halo star HD84937, Dr Sneden points out that observed chemical abundance levels do not always agree with prior abundance results for these elements (scandium through zinc) and ‘when carefully analyzed can be excellent measures of prior nucleosynthesis events’. This confirms metalpoor halo objects as perfect starting points for the development of galactic chemical evolution (GCE) theories. For this reason, further detailed investigations into metal-poor stars are required. This should be realised as results from largescale observation surveys are obtained. As Dr Sneden concludes: ‘additional precise abundance determinations in metal-poor halo stars should be undertaken; such studies may help to identify the nature of the first stars as well as to discover additional r-process-rich, ultra-metal-poor stars.’
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Detail More data is required to fine tune our understanding. What current, or forthcoming, sky surveys are planned for this purpose? The Gaia/ESO large spectroscopic survey will be a major step in the right direction, gathering more than 100,000 high resolution spectra of stars that will have very good parallaxes from the Gaia astrometric parallax mission. There are also several other current spectroscopic very large-sample studies that can take advantage of the Gaia database: e.g., APOGEE, a dedicated near-infrared (thus able to penetrate Galactic dust) survey, and GALAH, a wide wavelength-coverage spectroscopic survey of the Galactic disk and halo. What type of laboratory experiments are used in conjunction with astronomical observations? Abundances of elements in stellar atmospheres can be no more accurate than the input atomic transition data, particularly transition probabilities, for absorption lines that are seen in stellar spectra. We need these transition data for work on all kinds of stars, from metal-poor halo stars to metal-rich disk stars. Fortunately, the efforts of several laboratory atomic physics groups (in Wisconsin, London, Mons, and Lund, for example) have been rewarded in recent years with heightened accuracy in the basic lab data – which have instantly improved the stellar abundance results. How do chemical abundance levels vary between the outer halo region and the galactic plane? The dominant effect is the overall greatly diminished bulk levels of heavy elements in outer halo stars. Even though our Sun is composed of about 90% hydrogen and 9% helium, and the other 1% comprising
the entire set of heavy elements, our Sun qualifies as "metal-rich". Stars in the outer halo are more pristine H and He objects, with the heavy elements making up 1/10% down to about 1/1,000,000%. It is often difficult to detect the presence of any heavy elements in the spectra of halo stars. Just as interestingly, the relative abundances are often decidedly non-solar. For example we have detected r-process-rich and s-process-rich halos stars, ones with more lithium than our Sun has, and ones that are anomalously enhanced in carbon. Is chemical evolution witnessed when we observe entire galaxies back through time, at different cosmological epochs? Yes (see previous answer). Since the halo stars are so metal-weak, we believe that sometimes the elements in a halo-star's atmosphere might be the product of the lives and deaths of just a few (maybe even one) stars. This gives us direct insight into the nucleosynthetic process. We can look back in time but not forward. How do you expect the Milky Way to evolve into the future, and what will its final chemical state look like? The overall heavy element content will grow with time. It is a bit difficult to distinguish "super metal-rich stars" (those with larger heavy-element contents than our Sun) because the present solar chemical composition is the product of many prior stellar generations of element donors – one additional contribution won't change things that much. Nevertheless, there are several ongoing efforts to identify stars more metal-rich than our Sun, and to see if their relative abundance ratios are different than the Sun.
RESEARCH OBJECTIVES Dr Sneden’s research focuses on observational astronomy with an emphasis on ground-based stellar spectroscopy. His work is helping to inform our knowledge of how the chemical elements that make up our world came into being. FUNDING NSF and NASA COLLABORATORS • Caty Pilachowski (Indiana University) • Raffaele Gratton & colleagues (Padova Observatory) • Jim Lawler & colleagues (University of Wisconsin) • John Cowan (University of Oklahoma) BIO After a BA in Astronomy from Haverford College, Dr Chris Sneden completed his PhD in Astronomy at the University of Texas at Austin, where he is now Rex G. Baker, Jr. and McDonald Observatory Centennial Research Professor of Astronomy. He has published about 260 peer-reviewed articles with nearly 22,000 citations from these. CONTACT Chris Sneden Professor The University of Texas at Austin Department of Astronomy 2515 Speedway, RLM 13.116 Austin, Texas 78712-1205 USA T: +1 512 471 1349 E: chris@astro.as.utexas.edu W: http://www.as.utexas.edu/~chris/
The efforts of several laboratory atomic physics groups have been rewarded in recent years with heightened accuracy in the basic lab data
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The birth of a star is a violent and chaotic event, with gas flowing in and being ejected outwards at speeds up to hundreds of kilometres per second. The formation of a star is almost always accompanied by the formation of a planetary system
Astronomy
A star is born: understanding the physics of star formation Understanding the violent and chaotic processes that characterise the birth of new stars is one of the biggest challenges in contemporary astrophysics. While advances in infrared detection technologies have made it possible to observe aspects of the star formation process directly, there are still many mysteries surrounding the exact physics involved. Dr Christopher McKee, at the University of California at Berkeley, has been developing simulations to unravel these complex processes to understand exactly what triggers the formation of these celestial bodies.
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tars are born out of diffuse molecular clouds of gas, in regions of space known as ‘stellar nurseries’. These gas clouds contain the hydrogen and heavier elements that provide the fuel source for the star’s lifetime. These molecular clouds can be in an approximate equilibrium between the forces acting to expand the cloud and those trying to collapse it (primarily gravity). However, if this equilibrium is perturbed, either by an external force, such as a supernova explosion, or by the cloud becoming sufficiently massive, the molecular cloud begins to undergo gravitational collapse. While this collapse occurs, the cloud can fragment into smaller masses. As stellar-mass fragments collapse, the temperature rises, and eventually the hot gas inside is at a high enough pressure to stop further gravitational collapse. The star then begins its life as a protostar that continues to grow by accreting
The star-forming region Rho Ophiuchi is located just 400 light years from Earth. Image by Rogelio Bernal Andreo
the remaining mass from the fragment and possibly additional mass from the surrounding medium. Much of the gas that accretes onto the protostar does so through a disk, and planets can form during the late stages of this process. However, not all of these molecular clouds end up forming new stars, and not all the mass in a star-forming cloud goes into stars. What determines when and where stars form, and what determines their masses? The fundamental physical processes underlying star formation are only partially understood. These processes interact in complex ways that cannot be accurately described with pencil and paper calculations, and star formation can never be studied in the laboratory because gravity is too weak. This is why Dr Chris McKee and his team of researchers at the University of California at Berkeley are interested in finding ways to simulate these processes on supercomputers and further our understanding of both how and why these events occur. These simulations can take over 1000 hours on 1000 processors acting in parallel on a computer. However, even such enormous simulations cannot follow the full range of scales, from a
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Astronomy
Above and left: Images prepared by David Ellsworth and Tim Sandstrom from a simulation by Pak Shing Li showing 350,000 years of evolution of a giant molecular cloud. Right: A map of the amount of gas along each line of sight in a simulated filamentary molecular cloud that is hundreds of times more massive than the Sun, with a closeup view of the region where two parts of the cloud are colliding. The protostars that have formed are indicated by black circles.
Stars are rarely born as isolated individuals; instead entire clusters of stars might exist within one encompassing molecular gas cloud gas cloud light years in diameter to a star only light seconds across, so the accuracy of the simulations increases as computers become more powerful. THE SIZE OF STARS One aspect of star formation that Dr McKee is particularly interested in is the initial mass function (IMF). The IMF describes the initial distribution of masses in a newly formed stellar system, and what is very unusual about the IMF is that it appears to be about the same for almost all the stellar systems that have been observed. The IMF is of great interest to astrophysicists as, if it were well-understood, it would shed light on how the stars formed and on how
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the conditions under which stars form shape their future. Stars like the Sun live for about 10 billion years, the least massive stars, about a tenth the mass of the Sun, live 100 times longer, and the most massive stars live for only a few million years. Because massive stars live so briefly, they burn brightly and have a powerful effect on their surroundings, culminating in a gigantic explosion – a supernova. The IMF determines how much material will be locked up in long-lived stars and how much goes into the massive, shortlived stars that create the heavy elements. The typical star – one at the peak of the IMF – has a mass only a few tenths the mass of the Sun, and a question of particular importance is, what determines that mass? Recent work by Dr McKee and his collaborators suggests
that the observed peak in the IMF is due to heating by the accretion of matter onto the protostars, which limits the fragmentation processes in star formation. STELLAR CLUSTERS Most stars are formed in stellar clusters, which are groups of stars that are sufficiently close to feel the effects and forces of their neighbouring stars. These clusters can involve thousands of stars, and in extreme cases over a million stars. Clusters can be held together tightly by the effects of the gravitational force, or they can be more loosely bound, so that they dissolve as their natal gas is dissipated or when they intercept another molecular cloud.
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Detail RESEARCH OBJECTIVES Dr McKee’s research focuses on the scientific theory behind star formation. In particular, his research looks at the formation of both low-mass stars such as the sun and high-mass stars, the determining factors behind the rate of star formation in galaxies, and the processes governing the formation of the first stars in the universe. FUNDING • National Aeronautics and Space Administration (NASA) • National Science Foundation (NSF) PRINCIPAL COLLABORATORS • Richard Klein • Mark Krumholz • Pak Shing Li • Eve Ostriker • Jonathan Tan BIO Prof McKee completed a PhD in Physics at UC Berkeley in 1970. After several years as an assistant professor of Astronomy at Harvard University, he joined the Physics and Astronomy departments at UC Berkeley, where he has remained since 1974. Prof McKee is a member of the US National Academy of Sciences.
Dr McKee has been working on models to account for not just the formation of individual stars, but how entire clusters form. Just as there is an IMF for stars, there is an IMF for clusters that also needs to be understood. THE FIRST STARS The first stars in the universe formed shortly after the Big Bang out of gas that had no heavy elements such as carbon, oxygen and iron, all of which are made in supernovae that occur at the end of some stars’ lives. No stars without any heavy elements have ever been observed, which most likely means that the first stars were sufficiently massive – more than about 80% of the mass of the Sun – that they died before now. Another
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important difference between the first stars and subsequent generations of stars is that it is believed that during the initial stages of the formation of the first stars, it is the gravity of dark matter that initiates gravitational collapse. Calculations have shown that this naturally leads to more massive stars, but the IMF of these stars remains uncertain. Dr McKee and his collaborators are simulating the formation of the first stars in order to shed light on this problem.
CONTACT Professor Christopher McKee Department of Physics University of California-Berkeley Berkeley, CA USA E: cmckee@astro.berkeley.edu T: +1 510-642-5275 W: http://astro.berkeley.edu/facultyprofile/chris-mckee
All of Dr McKee’s work contributes towards a future in which it would be possible to accurately predict when and where stars are likely to form, and what the outcome will be. This work is part of the grand scientific quest to understand our origins
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COMMUNICATION RESEARCH NEWS
Video: The stats you need to know
The days of VHS tapes and the constantly moving screen when you hit the pause button seem a far-cry from the technological world of 2017. Video literally is everywhere you turn – TV, Facebook, interactive billboards, you name it. Love it or hate it, there is no denying that video will continue its dominance as the king of media into future years to come. Don’t believe me? Just check out some of the statistics below, and its widespread prevalence will soon become clear. • As of 2017, online video accounts for 74% of all online traffic • More than half of all marketing professionals state that video content provides the best return on investment • Video provides a 49% faster growth in revenue • People spend 2.6x longer on pages with video than without • YouTube – the world’s largest videosharing website – has over a billion users See what I mean? But, why is this important to you as a researcher? And how can you utilise video to your advantage? Here are my top tips, in line with current statistics, for getting you and your research noticed.
3. Share your video Email, social media, your personal website – unless you share your video around, it will not be seen. Make its online presence easy and obvious for potential watchers. 4. Keep updated People lose focus and get bored easily, so keeping them updated with fresh videos and information about your research is key to maintaining interest.
Until you have a video representing your research, you will not be able to reap the benefits of its use as a communication strategy
5. Utilise SEO This is a bit more complicated, but once you know how to do it, you’ll soon see the rewards. Using SEO keywords on your video helps with awareness, getting you and your research to the top of search engine results. For additional information on improving your online presence, please visit researchfeatures.com or sciani.com.
1. Create a video Obvious I know but, until you have a video representing your research, you will not be able to reap the benefits of its use as a communication strategy. 2. Keep your video short Nearly two-thirds of consumers prefer videos under 60 seconds long so being concise is vital. Condense your research down to get your key message across.
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